A model to calculate the thermodynamic functions of the pure metal nanocrystals has been developed, with the consideration of the effects of both the interfaces and the crystal in the nano-grain interior. As an exampl...A model to calculate the thermodynamic functions of the pure metal nanocrystals has been developed, with the consideration of the effects of both the interfaces and the crystal in the nano-grain interior. As an example, the enthalpy, entropy and Gibbs free energy, as functions of the excess free volume at interfaces, temperature and grain size, are calculated for the Co nanocrystals. Furthermore, the characteristics of β-Co→α-Co phase transformation are studied, and the transformation temperatures at different levels of grain size, as well as the critical grain sizes at different temperatures, are predicted. The calculation results show that, the nano-grained β-Co (fcc) is thermodynamically stable at temperatures much lower than that for the conventional coarse-grained materials, and may also stably exist at room temperature when the grain size is reduced to be small enough. The present model is verified by comparisons between the experimental findings and the theoretical predictions.展开更多
As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile...As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.展开更多
Raoultian activity coefficients γ0c of C in infinitely dilute Fe-C binary melts at temperatures of 1833, 1873, 1923, and 1973 K have been determined from the converted mass action concentrations Nc of C in Fe-C binar...Raoultian activity coefficients γ0c of C in infinitely dilute Fe-C binary melts at temperatures of 1833, 1873, 1923, and 1973 K have been determined from the converted mass action concentrations Nc of C in Fe-C binary melts by the developed AMCT-Ni model based on the atom-molecule coexistence theory (AMCT). The obtained expression of γ0c by the developed AMCT-Ni model has been evaluated to be accurate based on the reported ones from the literature. Meanwhile, three activity coefficients γc,f%,c, andfH,c of C coupled with activity aR,C or a%,c or aH,c have been obtained by the developed AMCT-Ni model and assessed through comparing with the predicted ones by other models from the literature. The first-order activity interaction coefficients ec, ec, and hcc related to γc f%,c, and fH,c are also determined and assessed in comparison with the reported ones from the literature. Furthermore, the integral molar mixing thermodynamic functions such as AmixHm,Fe-C, △mix-Sm,Fe-C, and △mixGm,Fe-C of Fe-C binary melts over a temperature range from 1833 to 1973 K have been determined and evaluated to be valid based on the determined ones from the literature.展开更多
We present a unified derivation of the pressure equation of states, thermodynamics and scaling functions for the one-dimensional (1D) strongly attractive Fermi gases with SU(w) symmetry. These physical quantities ...We present a unified derivation of the pressure equation of states, thermodynamics and scaling functions for the one-dimensional (1D) strongly attractive Fermi gases with SU(w) symmetry. These physical quantities provide a rigorous understanding on a universality class of quantum criticality characterized by the critical exponents z = 2 and correlation length exponent v= 1/2. Such a universality class of quantum criticality can occur when the Fermi sea of one branch of charge bound states starts to fill or becomes gapped at zero temperature. The quantum critical cone can be determined by the double peaks in specific heat, which serve to mark two crossover temperatures fanning out from the critical point. Our method opens to further study on quantum phases and phase transitions in strongly interacting fermions with large SU ( w) and non-SU ( w ) symmetries in one dimension.展开更多
Using the CALPHAD (Calculation of Phase Diagram) technique, the DyCl3-MCl (M = Na, K, Rb, Cs) systems were optimized and calculated. The modified quasi-chemical model in the pair approximation for short-range orde...Using the CALPHAD (Calculation of Phase Diagram) technique, the DyCl3-MCl (M = Na, K, Rb, Cs) systems were optimized and calculated. The modified quasi-chemical model in the pair approximation for short-range ordering was used to describe the Gibbs energies of the liquid phase in these systems. From the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized base on an interactive computer-assisted analysis. The optimized parameters and the experimental data were thermodynamically self-consistent. The optimized results were discussed.展开更多
Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O(s)were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurr...Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O(s)were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurred in the temperature range of T=368-374 K.The peak temperature of the dehydration was observed to be TD=(371.828±0.146)K by means of the heat-capacity measurement.The molar enthalpy and entropy of the dehydration were ΔDHm=(18.571±0.142)kJ/mol and ΔDSm=(49.946±0.415)J/(K·mol),respectively.The experimental values of heat capacities for the solid(Ⅰ)and the solid-liquid mixture(Ⅱ)were respectively fitted to two polynomial equations by the least square method.The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.展开更多
The crystal structure of ephedrine hydrochloride was determined by means of X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P21. Unit cell parameters are a=0.7308(6) n...The crystal structure of ephedrine hydrochloride was determined by means of X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P21. Unit cell parameters are a=0.7308(6) nm, b=0.6124(5) nm, and c= 1.2618(11) nm; β=90°, β= 102°, and γ =90°; Z=2. Low-temperature heat capacities of the title compound were measured with an improved precision automated adiabatic calorimeter over a temperature range from 77 K to 396 K. A polynomial equation of the heat capacities as a function of temperature in the temperature region was fitted by the least-squares. Based on the fitted polynomial equation, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at the intervals of 5 K.展开更多
The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular...The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound's structure-activity relationship.展开更多
A novel compound-monohydrated zinc nicotinate was prepared via room temperature solid phase synthesis and ball grinding.FTIR,chemical and elemental analyses and X-ray powder diffraction technique were applied to chara...A novel compound-monohydrated zinc nicotinate was prepared via room temperature solid phase synthesis and ball grinding.FTIR,chemical and elemental analyses and X-ray powder diffraction technique were applied to characterizing the structure and composition of the complex.Low-temperature heat capacities of the solid coordination compound were measured by a precision automated adiabatic calorimeter over a temperature range from 77 to 400 K.A solid-solid phase transition process occurred in a temperature range of 321―342 K inferred according to the heat capacity curve,and the peak temperature,molar enthalpy and entropy of the phase transition of monohydrated zinc nicotinate were determined to be Ttrs=(340.584±0.829) K,ΔtrsHm=(12.682±0.041) kJ/mol and ΔtrsSm=(37.235±0.101) KJ/mol).The experimental values of the molar heat capacities in the temperature regions of 77―321 K and 342―400 K were,respectively,fitted to two polynomial equations.In addition,the polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K.展开更多
The heat capacities of 3-( 2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (a racemic mixture, molar ratio of cis-/trans-structure is 35/65) in a temperature range from 78 to 389 K were measured with ...The heat capacities of 3-( 2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (a racemic mixture, molar ratio of cis-/trans-structure is 35/65) in a temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with a purity of 98.75% ( molar fraction). A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and en- tropy of fusion, △fusHm, △fusSm, of the acid were determined to be (331.48±0.03 ) K, (16.321±0.031) kJ/mol, and (49.24±0.19) J/( K·mol), respectively. The thermodynamic functions of the sample, Ht-H298.15, Sr-S298.15 and Gr-G298.15, were reported at a temperature intervals of 5 K. The thermal decomposition of the sample was studied using thermogravimetric(TG) analytic technique, the thermal decomposition starts at ca. 418 K and ends at ca. 544 K, the maximum decomposition rate was obtained at 510 K. The order of reaction, preexponential factor and activation energy are n =0.23, A =7.3 ×10^7 min^-1 , E =70.64 kJ/mol, respectively.展开更多
Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were ...Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q^-) and molecular average polarizability(α)).These models presented better correlations(r^2〉0.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.展开更多
DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as ...DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume(Cv),entropy(S),standard enthalpy of formation(ΔfH) and standard Gibbs free energy of formation(ΔfG).The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation(Δr,fG).It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.展开更多
Co_((1-x))ZnxFe_(2)O_(4)nanospheres(x=0,0.5,0.8)with a unidirectional cubic spinel structure were prepared by a solvothermal method.By using a range of theoretical and empirical models,the experimental heat capacity v...Co_((1-x))ZnxFe_(2)O_(4)nanospheres(x=0,0.5,0.8)with a unidirectional cubic spinel structure were prepared by a solvothermal method.By using a range of theoretical and empirical models,the experimental heat capacity values were fitted as a function of temperature over a suitable temperature range to explain the possible relationship between the magnetic properties and microstructure of the nanospheres.As a result,at a low temperature(T<10 K),the parameter Bfswdecreases with increasing Zn concentration,implying that the exchange interaction between A and B sites decreases.At a relatively high temperature(T>50 K),the Debye temperature decreases with increasing Zn concentration,which is due to the weakening of the interatomic bonding force after the addition of non-magnetic materials to the Co Fe_(2)O_(4)spinel ferrite.展开更多
Heat capacities of the rare-earth complex with glycine [Ho(Gly)3Cl3·3H2O] were measured with a high-precision automatic adiabatic calorimeter over the temperature range from 78 to 348 K.In the experimental temper...Heat capacities of the rare-earth complex with glycine [Ho(Gly)3Cl3·3H2O] were measured with a high-precision automatic adiabatic calorimeter over the temperature range from 78 to 348 K.In the experimental temperature range,the heat capacities increased in a smooth and continuous manner and no phase transition or thermal anomaly occurred.Therefore,the sample was stable in the above temperature range.The values of experimental heat capacities were fitted to a polynomial equation with least square method and ...展开更多
The heat capacities of D-galactose and galactitol were measured on a quantum design physical property measurement system(PPMS) over a temperature range of 1.9-300 K, and the experimental data were fitted to a functi...The heat capacities of D-galactose and galactitol were measured on a quantum design physical property measurement system(PPMS) over a temperature range of 1.9-300 K, and the experimental data were fitted to a function of T using a series of theoretical and empirical models in appropriate temperature ranges. The fit results were used to calculate thermodynamic function values, C^θp,m, ^T0S0^θm , and △^T0H^θm from 0 K to 300 K. The standard molar heat capacity, entropy and enthalpy values of D-galactose and galactitol at 298.15 K and 0.1 MPa were determined to be C^θp,m=(227.96±2.28) and(239.50±2.40) J·K^-1·mol^-1, S0^θm = (211.22±2.11) and (230.82±2.30) J·K^-1·mol^-1 and μm = (33.95±0.34) and (36.57±0.37) kJ/mol, respectively.展开更多
The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in Na...The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in NaF-AIF3 melts were calculated based upon this scheme. The thermodynamic mixing function for liquid NaF and solid AIF3, and liquidus data of NaF-AlF3 systems were calculated by using the above evaluated parameters. The results obtained are in good agreement with the experimental data.展开更多
In this paper,it was addressed a hydrogen absorbing and desorbing thermodynamics inα+βtype TC21 titanium alloy with high strength and toughness based on thermodynamic experiments and calculation.The relationship bet...In this paper,it was addressed a hydrogen absorbing and desorbing thermodynamics inα+βtype TC21 titanium alloy with high strength and toughness based on thermodynamic experiments and calculation.The relationship between concentration(C),temperature(T),and pressure(P)of TC21 alloy is shown by P-C-T curves during hydrogen absorption and desorption process,which were measured by multistep hydrogenation/dehydrogenation methods from 625 to 750℃.The P-C-T isotherms at a given temperature were separated into three regions.The partial thermodynamic functions of hydrogen reaction were evaluated by a modified form of Sievert’s law and P-CoTrelation of different regions was expressed by the modified Sievert’s law.The results show that the enthalpy of hydrogen reaction in the first and third region relies on hydrogen content.According to Vant’s Hoff law,enthalpy and entropy of hydrogenation platform in TC21 alloys are-53.58 kJ·mol^(-1)and-127.41 J·K·mol^(-1),respectively.Compared with P-C-T curves of hydrogen absorption,that of hydrogen desorption exists hysteresis.展开更多
n-Alkanes have been widely used as phase change materials(PCMs) for thermal energy storage applications because of their exceptional phase transition performance, high chemical stability, long term cyclic stability an...n-Alkanes have been widely used as phase change materials(PCMs) for thermal energy storage applications because of their exceptional phase transition performance, high chemical stability, long term cyclic stability and non-toxicity. However, the thermodynamic properties, especially heat capacity, of n-alkanes have rarely been comprehensively investigated in a wide temperature range, which would be insufficient for design and utilization of n-alkanes-based thermal energy storage techniques. In this study, the thermal properties of n-alkanes(C;H;-C;H;), such as thermal stability, thermal conductivity, phase transition temperature and enthalpy were systematically studied by different thermal analysis and calorimetry methods, and compared with previous results. Thermodynamic property of these n-alkanes was studied in a wide temperature range from 1.9 K to 370 K using a combined relaxation(Physical Property Measurement System, PPMS), differential scanning and adiabatic calorimetry method, and the corresponding thermodynamic functions, such as entropy and enthalpy, were calculated based on the heat capacity curve fitting. Most importantly, the heat capacities and related thermodynamic functions of n-heneicosane and n-docosane were reported for the first time in this work, as far as we know. This research work would provide accurate and reliable thermodynamic properties for further study of n-alkanes-based PCMs for thermal energy storage applications.展开更多
Rare earth elements have been widely used in many areas. Rare earth complex bearing an amino acid was synthesized to study the influence and the long term effect of rare earth elements on environment and human beings...Rare earth elements have been widely used in many areas. Rare earth complex bearing an amino acid was synthesized to study the influence and the long term effect of rare earth elements on environment and human beings, because amino acid is the basic unit of the living things. Previous work on these kinds of complex is focused on synthesis and characterization of them. But their thermodynamic data have seldom been reported. Here we present the thermodynamic study of [Ho(H 2O) 5]Cl 3. The heat capacity of Holmium complex with threonine, [Ho(Thr)(H 2O) 5]Cl 3 , was measured with an automatic adiabatic calorimeter in the temperature range from 79 K to 330 K and no thermal anomaly was found in this range. Thermodynamic functions relative to standard state 298 15 K were derived from the heat capacity data. Thermal decomposition behavior of the complex in nitrogen atmosphere in the range from 300 K to 900 K was studied by thermogravimetric (TG) technique and a possible decomposition mechanism was proposed according to the TG DTG results.展开更多
Thermochemistry is the study of the energy changes which occur during a chemi-cal reaction. For example, in the hydrolytic polymerization of Cr, Cr[Cr(OH)],Cr[Cr(OH)]and Cr[Cr(OH)]were formed at concentration ra...Thermochemistry is the study of the energy changes which occur during a chemi-cal reaction. For example, in the hydrolytic polymerization of Cr, Cr[Cr(OH)],Cr[Cr(OH)]and Cr[Cr(OH)]were formed at concentration range of 0.005-0.04展开更多
基金the National Natural Science Foundation of China(Grant No.50401001) the Prograrnof Beijing New Star of Science and Technology(Grant No.2004B04).
文摘A model to calculate the thermodynamic functions of the pure metal nanocrystals has been developed, with the consideration of the effects of both the interfaces and the crystal in the nano-grain interior. As an example, the enthalpy, entropy and Gibbs free energy, as functions of the excess free volume at interfaces, temperature and grain size, are calculated for the Co nanocrystals. Furthermore, the characteristics of β-Co→α-Co phase transformation are studied, and the transformation temperatures at different levels of grain size, as well as the critical grain sizes at different temperatures, are predicted. The calculation results show that, the nano-grained β-Co (fcc) is thermodynamically stable at temperatures much lower than that for the conventional coarse-grained materials, and may also stably exist at room temperature when the grain size is reduced to be small enough. The present model is verified by comparisons between the experimental findings and the theoretical predictions.
基金supported by the National Key R&D Program of China(2018YFC1900500)the Graduate Scientific Research and Innovation Foundation of Chongqing,China(Grant No.CYB20002).
文摘As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.
文摘Raoultian activity coefficients γ0c of C in infinitely dilute Fe-C binary melts at temperatures of 1833, 1873, 1923, and 1973 K have been determined from the converted mass action concentrations Nc of C in Fe-C binary melts by the developed AMCT-Ni model based on the atom-molecule coexistence theory (AMCT). The obtained expression of γ0c by the developed AMCT-Ni model has been evaluated to be accurate based on the reported ones from the literature. Meanwhile, three activity coefficients γc,f%,c, andfH,c of C coupled with activity aR,C or a%,c or aH,c have been obtained by the developed AMCT-Ni model and assessed through comparing with the predicted ones by other models from the literature. The first-order activity interaction coefficients ec, ec, and hcc related to γc f%,c, and fH,c are also determined and assessed in comparison with the reported ones from the literature. Furthermore, the integral molar mixing thermodynamic functions such as AmixHm,Fe-C, △mix-Sm,Fe-C, and △mixGm,Fe-C of Fe-C binary melts over a temperature range from 1833 to 1973 K have been determined and evaluated to be valid based on the determined ones from the literature.
基金Supported by the National Natural Science Foundation of China under Grant No 11374331the key NSFC under Grant No11534014partially supported by the Australian Research Council
文摘We present a unified derivation of the pressure equation of states, thermodynamics and scaling functions for the one-dimensional (1D) strongly attractive Fermi gases with SU(w) symmetry. These physical quantities provide a rigorous understanding on a universality class of quantum criticality characterized by the critical exponents z = 2 and correlation length exponent v= 1/2. Such a universality class of quantum criticality can occur when the Fermi sea of one branch of charge bound states starts to fill or becomes gapped at zero temperature. The quantum critical cone can be determined by the double peaks in specific heat, which serve to mark two crossover temperatures fanning out from the critical point. Our method opens to further study on quantum phases and phase transitions in strongly interacting fermions with large SU ( w) and non-SU ( w ) symmetries in one dimension.
基金Project supported by Key Project Foundation of Natural Science of Anhui Education Committee (2005KJ016ZD)
文摘Using the CALPHAD (Calculation of Phase Diagram) technique, the DyCl3-MCl (M = Na, K, Rb, Cs) systems were optimized and calculated. The modified quasi-chemical model in the pair approximation for short-range ordering was used to describe the Gibbs energies of the liquid phase in these systems. From the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized base on an interactive computer-assisted analysis. The optimized parameters and the experimental data were thermodynamically self-consistent. The optimized results were discussed.
基金Supported by the National Natural Science Foundation of China(No.20673050).
文摘Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O(s)were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurred in the temperature range of T=368-374 K.The peak temperature of the dehydration was observed to be TD=(371.828±0.146)K by means of the heat-capacity measurement.The molar enthalpy and entropy of the dehydration were ΔDHm=(18.571±0.142)kJ/mol and ΔDSm=(49.946±0.415)J/(K·mol),respectively.The experimental values of heat capacities for the solid(Ⅰ)and the solid-liquid mixture(Ⅱ)were respectively fitted to two polynomial equations by the least square method.The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.
基金Supported by the National Natural Science Foundation of China(Nos.20673050 and 20973089)
文摘The crystal structure of ephedrine hydrochloride was determined by means of X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P21. Unit cell parameters are a=0.7308(6) nm, b=0.6124(5) nm, and c= 1.2618(11) nm; β=90°, β= 102°, and γ =90°; Z=2. Low-temperature heat capacities of the title compound were measured with an improved precision automated adiabatic calorimeter over a temperature range from 77 K to 396 K. A polynomial equation of the heat capacities as a function of temperature in the temperature region was fitted by the least-squares. Based on the fitted polynomial equation, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at the intervals of 5 K.
基金Sponsored by the Youth Foundation for Natural Science from the Sichuan Provincial Education Department (No. 07ZB080)
文摘The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound's structure-activity relationship.
基金Supported by the National Natural Science Foundation of China(No.20673050)Key Project of Science Foundation from Shaanxi Educational College of China(No.08KJ017)
文摘A novel compound-monohydrated zinc nicotinate was prepared via room temperature solid phase synthesis and ball grinding.FTIR,chemical and elemental analyses and X-ray powder diffraction technique were applied to characterizing the structure and composition of the complex.Low-temperature heat capacities of the solid coordination compound were measured by a precision automated adiabatic calorimeter over a temperature range from 77 to 400 K.A solid-solid phase transition process occurred in a temperature range of 321―342 K inferred according to the heat capacity curve,and the peak temperature,molar enthalpy and entropy of the phase transition of monohydrated zinc nicotinate were determined to be Ttrs=(340.584±0.829) K,ΔtrsHm=(12.682±0.041) kJ/mol and ΔtrsSm=(37.235±0.101) KJ/mol).The experimental values of the molar heat capacities in the temperature regions of 77―321 K and 342―400 K were,respectively,fitted to two polynomial equations.In addition,the polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K.
基金Supported by the Education Bureau Science Foundation of Liaoning Province,China(No.20040261).
文摘The heat capacities of 3-( 2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (a racemic mixture, molar ratio of cis-/trans-structure is 35/65) in a temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with a purity of 98.75% ( molar fraction). A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and en- tropy of fusion, △fusHm, △fusSm, of the acid were determined to be (331.48±0.03 ) K, (16.321±0.031) kJ/mol, and (49.24±0.19) J/( K·mol), respectively. The thermodynamic functions of the sample, Ht-H298.15, Sr-S298.15 and Gr-G298.15, were reported at a temperature intervals of 5 K. The thermal decomposition of the sample was studied using thermogravimetric(TG) analytic technique, the thermal decomposition starts at ca. 418 K and ends at ca. 544 K, the maximum decomposition rate was obtained at 510 K. The order of reaction, preexponential factor and activation energy are n =0.23, A =7.3 ×10^7 min^-1 , E =70.64 kJ/mol, respectively.
基金supported by the Scientific Research Foundation of Guangxi Provincial Education Department (GJKY (2006) No 26)the Research Funds of Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment (0801K007, 0801K008)
文摘Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q^-) and molecular average polarizability(α)).These models presented better correlations(r^2〉0.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.
基金Sponsored by Natural Science Fundamental Research Program of Henan Provincial Education Department (No.2009A150022)Young Backbone Teacher Program of Xinyang Normal University
文摘DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume(Cv),entropy(S),standard enthalpy of formation(ΔfH) and standard Gibbs free energy of formation(ΔfG).The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation(Δr,fG).It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.
基金Basic Research Project of Liaoning Provincial Department of Education(No.LJKMZ20220829)Guangxi Key Laboratory of Information Materials(Guilin University of Electronic Technology)(No.211006-K)。
文摘Co_((1-x))ZnxFe_(2)O_(4)nanospheres(x=0,0.5,0.8)with a unidirectional cubic spinel structure were prepared by a solvothermal method.By using a range of theoretical and empirical models,the experimental heat capacity values were fitted as a function of temperature over a suitable temperature range to explain the possible relationship between the magnetic properties and microstructure of the nanospheres.As a result,at a low temperature(T<10 K),the parameter Bfswdecreases with increasing Zn concentration,implying that the exchange interaction between A and B sites decreases.At a relatively high temperature(T>50 K),the Debye temperature decreases with increasing Zn concentration,which is due to the weakening of the interatomic bonding force after the addition of non-magnetic materials to the Co Fe_(2)O_(4)spinel ferrite.
基金supported by the National Natural Science Foundation of China(20373072,20753002)
文摘Heat capacities of the rare-earth complex with glycine [Ho(Gly)3Cl3·3H2O] were measured with a high-precision automatic adiabatic calorimeter over the temperature range from 78 to 348 K.In the experimental temperature range,the heat capacities increased in a smooth and continuous manner and no phase transition or thermal anomaly occurred.Therefore,the sample was stable in the above temperature range.The values of experimental heat capacities were fitted to a polynomial equation with least square method and ...
基金Supported by the National Natural Science Foundation of China(No.21473198).
文摘The heat capacities of D-galactose and galactitol were measured on a quantum design physical property measurement system(PPMS) over a temperature range of 1.9-300 K, and the experimental data were fitted to a function of T using a series of theoretical and empirical models in appropriate temperature ranges. The fit results were used to calculate thermodynamic function values, C^θp,m, ^T0S0^θm , and △^T0H^θm from 0 K to 300 K. The standard molar heat capacity, entropy and enthalpy values of D-galactose and galactitol at 298.15 K and 0.1 MPa were determined to be C^θp,m=(227.96±2.28) and(239.50±2.40) J·K^-1·mol^-1, S0^θm = (211.22±2.11) and (230.82±2.30) J·K^-1·mol^-1 and μm = (33.95±0.34) and (36.57±0.37) kJ/mol, respectively.
文摘The scheme of dissociation of cryolite in NaF-AlF3 melts was proposed. The constants and heats of dissociation for cryolite were evaluated from experimental data. The mole fractions of each kind of ions at 1298K in NaF-AIF3 melts were calculated based upon this scheme. The thermodynamic mixing function for liquid NaF and solid AIF3, and liquidus data of NaF-AlF3 systems were calculated by using the above evaluated parameters. The results obtained are in good agreement with the experimental data.
基金the Key Program in Xihua University(No.Z1120117)Department of Education Research Fund in China,Sichuan Province(No.12201453)the Open Research Fund of Key Laboratory of Special Materials and Preparation Technology,Xihua University(No.S2jj2012-019)。
文摘In this paper,it was addressed a hydrogen absorbing and desorbing thermodynamics inα+βtype TC21 titanium alloy with high strength and toughness based on thermodynamic experiments and calculation.The relationship between concentration(C),temperature(T),and pressure(P)of TC21 alloy is shown by P-C-T curves during hydrogen absorption and desorption process,which were measured by multistep hydrogenation/dehydrogenation methods from 625 to 750℃.The P-C-T isotherms at a given temperature were separated into three regions.The partial thermodynamic functions of hydrogen reaction were evaluated by a modified form of Sievert’s law and P-CoTrelation of different regions was expressed by the modified Sievert’s law.The results show that the enthalpy of hydrogen reaction in the first and third region relies on hydrogen content.According to Vant’s Hoff law,enthalpy and entropy of hydrogenation platform in TC21 alloys are-53.58 kJ·mol^(-1)and-127.41 J·K·mol^(-1),respectively.Compared with P-C-T curves of hydrogen absorption,that of hydrogen desorption exists hysteresis.
基金the financial support from the National Nature Science Foundation of China (No. 22003065)Liaoning Provincial Natural Science Foundation of China (No. 2019-MS-318)+3 种基金Science and Technology Major Project of Liaoning Province (No. 2019JH1/10300002)the Scientific Instrument Developing Project of the Chinese Academy of Sciences (No. YJKYYQ20190046)Dalian Institute of Chemical Physics (No. DICP I202036)Dalian Outstanding Young Scientific Talent Program (No. 2019RJ10)。
文摘n-Alkanes have been widely used as phase change materials(PCMs) for thermal energy storage applications because of their exceptional phase transition performance, high chemical stability, long term cyclic stability and non-toxicity. However, the thermodynamic properties, especially heat capacity, of n-alkanes have rarely been comprehensively investigated in a wide temperature range, which would be insufficient for design and utilization of n-alkanes-based thermal energy storage techniques. In this study, the thermal properties of n-alkanes(C;H;-C;H;), such as thermal stability, thermal conductivity, phase transition temperature and enthalpy were systematically studied by different thermal analysis and calorimetry methods, and compared with previous results. Thermodynamic property of these n-alkanes was studied in a wide temperature range from 1.9 K to 370 K using a combined relaxation(Physical Property Measurement System, PPMS), differential scanning and adiabatic calorimetry method, and the corresponding thermodynamic functions, such as entropy and enthalpy, were calculated based on the heat capacity curve fitting. Most importantly, the heat capacities and related thermodynamic functions of n-heneicosane and n-docosane were reported for the first time in this work, as far as we know. This research work would provide accurate and reliable thermodynamic properties for further study of n-alkanes-based PCMs for thermal energy storage applications.
基金theNationalNaturalScienceFoundationofChina (No .2 0 0 73 0 47)
文摘Rare earth elements have been widely used in many areas. Rare earth complex bearing an amino acid was synthesized to study the influence and the long term effect of rare earth elements on environment and human beings, because amino acid is the basic unit of the living things. Previous work on these kinds of complex is focused on synthesis and characterization of them. But their thermodynamic data have seldom been reported. Here we present the thermodynamic study of [Ho(H 2O) 5]Cl 3. The heat capacity of Holmium complex with threonine, [Ho(Thr)(H 2O) 5]Cl 3 , was measured with an automatic adiabatic calorimeter in the temperature range from 79 K to 330 K and no thermal anomaly was found in this range. Thermodynamic functions relative to standard state 298 15 K were derived from the heat capacity data. Thermal decomposition behavior of the complex in nitrogen atmosphere in the range from 300 K to 900 K was studied by thermogravimetric (TG) technique and a possible decomposition mechanism was proposed according to the TG DTG results.
基金Project supported by the Natural Science Foundation of Shandong Province.
文摘Thermochemistry is the study of the energy changes which occur during a chemi-cal reaction. For example, in the hydrolytic polymerization of Cr, Cr[Cr(OH)],Cr[Cr(OH)]and Cr[Cr(OH)]were formed at concentration range of 0.005-0.04