Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydrox...Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">•</span> (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">•</span> radicals are determined by the energies <em>E<sub>orb</sub></em> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |<em>E<sub>orb</sub></em>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.展开更多
The transition state(TS) and Intrinsic Reaction Coordinate (IRC) for the titled reaction were traced by means of MCSCF/6-31G (210 configurations). The reaction activation energy of this reaction is 140.2KJ/mol. The re...The transition state(TS) and Intrinsic Reaction Coordinate (IRC) for the titled reaction were traced by means of MCSCF/6-31G (210 configurations). The reaction activation energy of this reaction is 140.2KJ/mol. The reaction rate constants of five temperetures were calculated by CVT involving the tunneling effects.展开更多
The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>...The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.展开更多
A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can...A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.展开更多
The kinetics and mechanisms of H abstraction reaction between isoflurane and a CI atom have been investigated using DFT and G3（MP2） methods of theory. The geometrical structures of all species were optimized by the ...The kinetics and mechanisms of H abstraction reaction between isoflurane and a CI atom have been investigated using DFT and G3（MP2） methods of theory. The geometrical structures of all species were optimized by the wB97XD/6-311＋＋G＊＊ method. Intrinsic reaction coordinate （IRC） analysis has been carried out for the reaction channels. Thermochemistry data have been obtained by utilizing the high accurate model chemistry method G3（MP2） combined with the standard statistical thermodynamic calculations. Gibbs free energies were used for reaction channels analysis. Two channels were obtained, which correspond to P（1） and P（2）. The rate constants for the two channels over a wide temperature range of 200-2000 K were also obtained. The results show that the barriers of P（1） and P（2） reaction channels are 50.36 and 50.34 kJ/mol, respectively, predicting that it exists two competitive channels. The calculated rate constant is in good agreement with the experiment value. Additionally, the results also show that the rate constants also increase from 1.85x10^-16 to 2.16x 10^12 cm3.moleculel.s-1 from 200 to 2000 K展开更多
After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated ...After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated by the perturbed degeneration theory and the Fermi golden rule,, the rate constant is gotten. Compared with the experimental results, it is satisfactory.展开更多
A single-sweep oscillopolarographic procedure is descrital which allows detethenahon of rateconstants for reachons of oH. For a wide range of compounds, the results fit well with rate constantspreviously obtained with...A single-sweep oscillopolarographic procedure is descrital which allows detethenahon of rateconstants for reachons of oH. For a wide range of compounds, the results fit well with rate constantspreviously obtained with other methods. Rate constants for reactions of six kinds of active compoundscontalned in rheum, a tradihonal Chinese herb, have been deteboned by this method. Rcationmechanism ha5 also been discussed.展开更多
A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any po...A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any point of reaction coordinate was calculated by counting the numberof quantum states and applied to determine the dividing surfaces along the intrinsic reaction coor-dinate (IRC). The classical exchange reaction H2+H, as an example, was investigated. The IRC forthe reaction has been traced and detailed information of IRC was carried out at the QCISD/6-311 G** level .The calculated rate constants are well consistent with the experimental results.展开更多
针对我国国产反应堆严重事故分析程序的发展需要,西安交通大学开发了一体化严重事故分析程序(modular severe accident analysis program,MOSAP)。为了验证MOSAP程序在再淹没期间相关模型的合理性和准确性,以QUENCH-06实验为例,利用MOSA...针对我国国产反应堆严重事故分析程序的发展需要,西安交通大学开发了一体化严重事故分析程序(modular severe accident analysis program,MOSAP)。为了验证MOSAP程序在再淹没期间相关模型的合理性和准确性,以QUENCH-06实验为例,利用MOSAP程序对实验进行建模,并将MOSAP程序的计算结果与实验结果以及国际通用程序的计算结果进行了对比。结果表明,对于包壳轴向温度、包壳氧化层厚度和氢气产量,MOSAP程序计算结果与实验值和国际通用程序计算结果符合良好。在计算包壳轴向温度和氧化层厚度方面,MOSAP程序计算结果优于国际通用程序计算结果。文中结论对MOSAP程序堆内模块验证和整个模块的验证具有一定的参考意义。展开更多
Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of...Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of TiH2 powder and aluminum melt was studied. The results show that the-time curves have three regions; in the first and second regions, the rate of reaction conforms zero and one order, respectively; in the third region, the hydrogen gas pressure remains constant and the rate of reaction reaches zero. The main factors that control the rate of reaction in the first and second regions are the penetration of hydrogen atoms in the titanium lattice and the chemical reaction between molten aluminum and titanium, respectively. According to the main factors that control the rate of reaction, three temperature ranges are considered for the reaction mechanism： （a） 700-750°C, （b） 750-800°C, and （c） 800-1000°C. In the first temperature range, the reaction is mostly under the control of chemical reaction; at the temperature range of 750 to 800°C, the reaction is controlled by the diffusion and chemical reaction; at the third temperature range （800-1000°C）, the dominant controlling mechanism is diffusion.展开更多
The kinetics of the catalytic reforming reaction of methane with carbondioxide to produce synthesis gas on a Ni/α-Al_2O_3 and a HSD-2 type commercial catalyst has beenstudied. The results indicate that the reaction o...The kinetics of the catalytic reforming reaction of methane with carbondioxide to produce synthesis gas on a Ni/α-Al_2O_3 and a HSD-2 type commercial catalyst has beenstudied. The results indicate that the reaction orders are one and zero for methane and carbondioxide, respectively, when the carbon dioxide partial pressure was about 12.5-30.0 kPa and thetemperature was at 1123-1173 K. However, when the carbon dioxide partial pressure was changed to30.0-45.0 kPa under the same temperature range of 1123-1173 K, the reaction orders of methane andcarbon dioxide are one. Furthermore, average rate constants at different temperatures weredetermined.展开更多
The reaction mechanism of SiCl4 with H2 has been studied theoretically using Gaussian 98 program at B3LYP/6-311G^＊ level. Three different reaction paths （a, b, c） in the gas phase were obtained. The geometries, vib...The reaction mechanism of SiCl4 with H2 has been studied theoretically using Gaussian 98 program at B3LYP/6-311G^＊ level. Three different reaction paths （a, b, c） in the gas phase were obtained. The geometries, vibrational frequencies and energies of every stagnation point in the reaction channel were calculated and the mechanisms have been confirmed. The results show that path a has an activation energy of 79.12 kcal/mol, which was considered as the main reaction path. Comparably, paths b and c have the energy barriers of 125.07 and 136.25 kcal/mol, respectively. The reaction rate constant was calculated by TST method over a wide temperature range of 900～1600 K, which further confirmed that path a was the main reaction channel展开更多
Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabi...Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabilities dramatically increase near the zero collision energy and then slightly decrease with increasing collision energy, which corresponds well to the behavior of a barrierless reaction. The effects of reagent HBr excitation were examined, it is shown that both the vibrational and the rotational excitations of reagent HBr have a negative effect on the reactivity of F ＋ HBr. The integral cross-section for the ground state of the reagent HBr decreases at a low collision energy and then becomes plat with increasing collision energy, which is reasonable for the feasibility of such an exothermal reaction. The rate constant that was obtained is slightly higher than that obtained in the quasi-classical trajectory calculation.展开更多
文摘Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">•</span> (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">•</span> radicals are determined by the energies <em>E<sub>orb</sub></em> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |<em>E<sub>orb</sub></em>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.
文摘The transition state(TS) and Intrinsic Reaction Coordinate (IRC) for the titled reaction were traced by means of MCSCF/6-31G (210 configurations). The reaction activation energy of this reaction is 140.2KJ/mol. The reaction rate constants of five temperetures were calculated by CVT involving the tunneling effects.
文摘The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.
基金Supported by the National Natural Science Foundation of China (No. 20076022).
文摘A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.
基金financed by the Natural Science Foundation of Shaanxi Province(2014JM2046,2013JQ2027)the Special Natural Science Foundation of Science and Technology Bureau of Xi’an City Government(CXY1443WL03,CXY1352WL19 and CXY1352WL20)+1 种基金National Science Foundation of China(21303135)the Industrial research project of Science and Technology Department of Shaanxi Province(2013K09-25)
文摘The kinetics and mechanisms of H abstraction reaction between isoflurane and a CI atom have been investigated using DFT and G3（MP2） methods of theory. The geometrical structures of all species were optimized by the wB97XD/6-311＋＋G＊＊ method. Intrinsic reaction coordinate （IRC） analysis has been carried out for the reaction channels. Thermochemistry data have been obtained by utilizing the high accurate model chemistry method G3（MP2） combined with the standard statistical thermodynamic calculations. Gibbs free energies were used for reaction channels analysis. Two channels were obtained, which correspond to P（1） and P（2）. The rate constants for the two channels over a wide temperature range of 200-2000 K were also obtained. The results show that the barriers of P（1） and P（2） reaction channels are 50.36 and 50.34 kJ/mol, respectively, predicting that it exists two competitive channels. The calculated rate constant is in good agreement with the experiment value. Additionally, the results also show that the rate constants also increase from 1.85x10^-16 to 2.16x 10^12 cm3.moleculel.s-1 from 200 to 2000 K
文摘After the electron transfers from the metal electrode to the Fe3+(H2O)(6) ion, the free energy of activation of this electron transfer reaction is calculated, then using the transition probability which is calculated by the perturbed degeneration theory and the Fermi golden rule,, the rate constant is gotten. Compared with the experimental results, it is satisfactory.
文摘A single-sweep oscillopolarographic procedure is descrital which allows detethenahon of rateconstants for reachons of oH. For a wide range of compounds, the results fit well with rate constantspreviously obtained with other methods. Rate constants for reactions of six kinds of active compoundscontalned in rheum, a tradihonal Chinese herb, have been deteboned by this method. Rcationmechanism ha5 also been discussed.
文摘A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any point of reaction coordinate was calculated by counting the numberof quantum states and applied to determine the dividing surfaces along the intrinsic reaction coor-dinate (IRC). The classical exchange reaction H2+H, as an example, was investigated. The IRC forthe reaction has been traced and detailed information of IRC was carried out at the QCISD/6-311 G** level .The calculated rate constants are well consistent with the experimental results.
文摘针对我国国产反应堆严重事故分析程序的发展需要,西安交通大学开发了一体化严重事故分析程序(modular severe accident analysis program,MOSAP)。为了验证MOSAP程序在再淹没期间相关模型的合理性和准确性,以QUENCH-06实验为例,利用MOSAP程序对实验进行建模,并将MOSAP程序的计算结果与实验结果以及国际通用程序的计算结果进行了对比。结果表明,对于包壳轴向温度、包壳氧化层厚度和氢气产量,MOSAP程序计算结果与实验值和国际通用程序计算结果符合良好。在计算包壳轴向温度和氧化层厚度方面,MOSAP程序计算结果优于国际通用程序计算结果。文中结论对MOSAP程序堆内模块验证和整个模块的验证具有一定的参考意义。
文摘Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of TiH2 powder and aluminum melt was studied. The results show that the-time curves have three regions; in the first and second regions, the rate of reaction conforms zero and one order, respectively; in the third region, the hydrogen gas pressure remains constant and the rate of reaction reaches zero. The main factors that control the rate of reaction in the first and second regions are the penetration of hydrogen atoms in the titanium lattice and the chemical reaction between molten aluminum and titanium, respectively. According to the main factors that control the rate of reaction, three temperature ranges are considered for the reaction mechanism： （a） 700-750°C, （b） 750-800°C, and （c） 800-1000°C. In the first temperature range, the reaction is mostly under the control of chemical reaction; at the temperature range of 750 to 800°C, the reaction is controlled by the diffusion and chemical reaction; at the third temperature range （800-1000°C）, the dominant controlling mechanism is diffusion.
文摘The kinetics of the catalytic reforming reaction of methane with carbondioxide to produce synthesis gas on a Ni/α-Al_2O_3 and a HSD-2 type commercial catalyst has beenstudied. The results indicate that the reaction orders are one and zero for methane and carbondioxide, respectively, when the carbon dioxide partial pressure was about 12.5-30.0 kPa and thetemperature was at 1123-1173 K. However, when the carbon dioxide partial pressure was changed to30.0-45.0 kPa under the same temperature range of 1123-1173 K, the reaction orders of methane andcarbon dioxide are one. Furthermore, average rate constants at different temperatures weredetermined.
基金This work was supported by the Foundation of Education Committee of Liaoning Province (No.990321076)
文摘The reaction mechanism of SiCl4 with H2 has been studied theoretically using Gaussian 98 program at B3LYP/6-311G^＊ level. Three different reaction paths （a, b, c） in the gas phase were obtained. The geometries, vibrational frequencies and energies of every stagnation point in the reaction channel were calculated and the mechanisms have been confirmed. The results show that path a has an activation energy of 79.12 kcal/mol, which was considered as the main reaction path. Comparably, paths b and c have the energy barriers of 125.07 and 136.25 kcal/mol, respectively. The reaction rate constant was calculated by TST method over a wide temperature range of 900～1600 K, which further confirmed that path a was the main reaction channel
基金Supported by the Open Project Program of Key Laboratory of Advanced Materials &Rheological Properties, Ministry of Educa-tion, China(No KF0504)
文摘Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabilities dramatically increase near the zero collision energy and then slightly decrease with increasing collision energy, which corresponds well to the behavior of a barrierless reaction. The effects of reagent HBr excitation were examined, it is shown that both the vibrational and the rotational excitations of reagent HBr have a negative effect on the reactivity of F ＋ HBr. The integral cross-section for the ground state of the reagent HBr decreases at a low collision energy and then becomes plat with increasing collision energy, which is reasonable for the feasibility of such an exothermal reaction. The rate constant that was obtained is slightly higher than that obtained in the quasi-classical trajectory calculation.
