Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, res...Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.展开更多
The excited-state intramolecular proton transfer(ESIPT) mechanisms of 2-(2-hydroxyphenyl)-4-phenylthiazole(HPT) and 2-(5-bromo-2-hydroxyphenyl)-4-phenylthiazole(BrHPT) have been systematically investigated by density ...The excited-state intramolecular proton transfer(ESIPT) mechanisms of 2-(2-hydroxyphenyl)-4-phenylthiazole(HPT) and 2-(5-bromo-2-hydroxyphenyl)-4-phenylthiazole(BrHPT) have been systematically investigated by density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods, approaching along with the polarizable continuum model(PCM). The calculated primary bond lengths and bond angles demonstrate that HPT and BrHPT can form intramolecular hydrogen bonds in the ground state(S0), which can be significantly strengthened in the first excited state(S1). Our calculated results well reproduce the experimental absorption and emission spectra. Upon addition of F-, the proton can move close to F-and the hydroxy moieties are deprotonated, which cause a red-shift in absorption and a new emission peak in fluorescence emission with the disappearance of the dual fluorescence emission. The calculated Mulliken’s charge distribution and frontier molecular orbitals further demonstrate that the ESIPT processes are more likely to occur in the S1 state. The constructed potential energy curves of the S0 and S1 states confirm that the proton transfer processes are hard to occur in the S0 state due to the high energy barriers. Moreover, much lower energy barriers are found in the S1 state, which proves that the ESIPT processes are more likely to take place in the S1 state. In addition, compound with electron withdrawing(-Br) group might result in much stronger intramolecular hydrogen bond and owns lower energy barrier, which can facilitate the ESIPT processes.展开更多
Density functional theory calculations at the B3LYP/6-31+G^** and B3LYP/6-311++G ^** levels were perfonned on thermal decomposition of 5,5′-bis(tetrazole)-1 ,r-diolate(TKX-50) anion with an intramolecular oxygen tran...Density functional theory calculations at the B3LYP/6-31+G^** and B3LYP/6-311++G ^** levels were perfonned on thermal decomposition of 5,5′-bis(tetrazole)-1 ,r-diolate(TKX-50) anion with an intramolecular oxygen transfer being an initial step. Tlie results show that the intramolecular oxygen transfers are the rate-limiting steps for the decomposition of title anion with activation energies being in the range of 287-328 kJ/mol. Judged by the nucleus- independent chemical shift values, the formation of antiaromatic ring in transition state or the decrease of aromaticity of the tetrazole ring of the reactant makes somewhat contribution to the high potential energies of the rate-limiting transition states. However, the activation energies of the following N2 elimination tlirough various pathways are in a low range of 136-166 kJ/mol. The tetrazole ring acts as an electron donor or acceptor in difierent pathways to assist the bond nipture or group elimination. The rate constants in a temperature range of 500-2000 K for all the intramolecular oxygen transferring reactions were obtained. The corresponding linear relationships between InA and 1/T were established.展开更多
The geometric and electronic structures of the derivatives of 4-nitro-5-(5-nitroimino-1,2,4-triazol-3-yl)-2H-1,2,3-triazolate(named A~J)are explored employing density functional theory(DFT)calculations at the B3LYP/6-...The geometric and electronic structures of the derivatives of 4-nitro-5-(5-nitroimino-1,2,4-triazol-3-yl)-2H-1,2,3-triazolate(named A~J)are explored employing density functional theory(DFT)calculations at the B3LYP/6-311G^(**)level of theory.Based on the optimized molecular structures,the heats of formation(HOF)are obtained,and the electronic properties,density and molecular sensitivity by characteristic heights(H_(50))are discussed.Besides,the detonation performances(detonation velocity,detonation pressure)are estimated via Kamlet-Jacobs(K-J)formula.Compounds B(H50=29.4 cm,ρ=1.91 g/cm^(3),Q=1563.04 cal/g,P=36.05 GPa,D=8.95 km/s)and H(H_(50)=31.9 cm,ρ=1.80 g/cm^(3),Q=1610.09 cal/g,P=37.31 GPa,D=9.12 km/s)have positive HOFs and remarkable insensitivity and good detonation performance,strongly suggesting them as the acceptable new-type explosive.The initiating power surpasses conventional primary explosives,such as HMX.The outstanding detonation power of compounds B and H contributes to its future prospects as a promising green primary explosive.展开更多
The structures and hydrogen storage properties of sodium atoms decorated B6 clusters are investigated by the B3LYP method with a 6-311＋G （d, p） basis set. For NamB6 （m = 1-3） clusters, Na atoms are always incline...The structures and hydrogen storage properties of sodium atoms decorated B6 clusters are investigated by the B3LYP method with a 6-311＋G （d, p） basis set. For NamB6 （m = 1-3） clusters, Na atoms are always inclined to separate far enough from each other and not cluster together on a B6 cluster surface so that each Na atom has sufficient space to bind hydrogen molecules. The hydrogen storage gravimetric density of a two Na atoms decorated B6 cluster is 17.91 wt% with an adsorption energy per H2 molecule （AAE/H2） of 0.6851 kcal.mo1^-1. The appropriate AAE/H2 and preferable gravimetric density of the two Na atoms decorated B6 cluster complex indicate that it is feasible for hydrogen storage application in ambient conditions.展开更多
Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with comp...Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with computer image analysis (CIA) and the transition of shear yielding zone (A_(sh)) with rubber volume fraction (V_f) was also manipulated. Results showed that the B-D transition of impact strength of blends corresponded to the fracture mechanism in PP/EPDM blends, from matrix crazing to matrix shear yielding. In addition, two new parameters, density of energy dissipation for crazing zone (F_(cz)) and for shear yielding zone (F_(sh)), are first obtained in this paper. The value of F_(sh) is about four times larger than that of F_(cz) for PP/EPDM blends, which confirmed that the matrix shear yielding is a more effective way of energy dissipation in blends.展开更多
Nighttime enhancements in ionospheric electron density at mid- and low-latitudes are investigated by using the critical frequency of the F2-1ayer （foF2） data measured from ionosonde stations at Okinawa （26.3°N...Nighttime enhancements in ionospheric electron density at mid- and low-latitudes are investigated by using the critical frequency of the F2-1ayer （foF2） data measured from ionosonde stations at Okinawa （26.3°N, 127.8°E, Geomagnetic 15.3°N）, Yamagawa （31.2°N, 130.6°E, Geomagnetic 20.4°N）, Kokubunji （35.7°N, 139.5°E, Geomagnetic 25.5°N）, and Wakkanai （45.4°N, 141.7°E, Geomagnetic 35.4°N） in East Asia during several solar cycles. The results show that there are obvious seasonal and solar activity dependencies of the nighttime electron density enhancements. The enhancements are termed pre-midnight enhancement and post-midnight enhancement, according to the local time when the enhancement appeared. The former has a higher occurrence probability in summer months than in winter months. In contrast, the latter has a larger occurrence probability in winter months than in summer months. Moreover, the nighttime enhancements in electron density are more likely to occur at lower solar activity. These seasonal and solar activity variations of the nighttime enhancements in electron density can be explained in terms of the combined effects of downward plasma flux from the plasmasphere and the neutral winds.展开更多
基金This work was supported by the Natural Science Foundation of Shandong Province (Y2002G11)
文摘Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.
基金supported by the National Natural Science Foundation of China (No. 21963008)the Natural Science Foundation of Hubei Province(No. 2016CFB400)the College Students’ Innovative Entrepreneurial Training Plan Program of Hubei Minzu University (Nos. 2016CX066 and X201910517140)。
文摘The excited-state intramolecular proton transfer(ESIPT) mechanisms of 2-(2-hydroxyphenyl)-4-phenylthiazole(HPT) and 2-(5-bromo-2-hydroxyphenyl)-4-phenylthiazole(BrHPT) have been systematically investigated by density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods, approaching along with the polarizable continuum model(PCM). The calculated primary bond lengths and bond angles demonstrate that HPT and BrHPT can form intramolecular hydrogen bonds in the ground state(S0), which can be significantly strengthened in the first excited state(S1). Our calculated results well reproduce the experimental absorption and emission spectra. Upon addition of F-, the proton can move close to F-and the hydroxy moieties are deprotonated, which cause a red-shift in absorption and a new emission peak in fluorescence emission with the disappearance of the dual fluorescence emission. The calculated Mulliken’s charge distribution and frontier molecular orbitals further demonstrate that the ESIPT processes are more likely to occur in the S1 state. The constructed potential energy curves of the S0 and S1 states confirm that the proton transfer processes are hard to occur in the S0 state due to the high energy barriers. Moreover, much lower energy barriers are found in the S1 state, which proves that the ESIPT processes are more likely to take place in the S1 state. In addition, compound with electron withdrawing(-Br) group might result in much stronger intramolecular hydrogen bond and owns lower energy barrier, which can facilitate the ESIPT processes.
文摘Density functional theory calculations at the B3LYP/6-31+G^** and B3LYP/6-311++G ^** levels were perfonned on thermal decomposition of 5,5′-bis(tetrazole)-1 ,r-diolate(TKX-50) anion with an intramolecular oxygen transfer being an initial step. Tlie results show that the intramolecular oxygen transfers are the rate-limiting steps for the decomposition of title anion with activation energies being in the range of 287-328 kJ/mol. Judged by the nucleus- independent chemical shift values, the formation of antiaromatic ring in transition state or the decrease of aromaticity of the tetrazole ring of the reactant makes somewhat contribution to the high potential energies of the rate-limiting transition states. However, the activation energies of the following N2 elimination tlirough various pathways are in a low range of 136-166 kJ/mol. The tetrazole ring acts as an electron donor or acceptor in difierent pathways to assist the bond nipture or group elimination. The rate constants in a temperature range of 500-2000 K for all the intramolecular oxygen transferring reactions were obtained. The corresponding linear relationships between InA and 1/T were established.
基金the of Tangshan Normal University(2021B37and 2021B32)the School Fund of Shanxi Institute of Technology(2019004)the Fund of Shanxi Provincial Education Department(2019L0986)。
文摘The geometric and electronic structures of the derivatives of 4-nitro-5-(5-nitroimino-1,2,4-triazol-3-yl)-2H-1,2,3-triazolate(named A~J)are explored employing density functional theory(DFT)calculations at the B3LYP/6-311G^(**)level of theory.Based on the optimized molecular structures,the heats of formation(HOF)are obtained,and the electronic properties,density and molecular sensitivity by characteristic heights(H_(50))are discussed.Besides,the detonation performances(detonation velocity,detonation pressure)are estimated via Kamlet-Jacobs(K-J)formula.Compounds B(H50=29.4 cm,ρ=1.91 g/cm^(3),Q=1563.04 cal/g,P=36.05 GPa,D=8.95 km/s)and H(H_(50)=31.9 cm,ρ=1.80 g/cm^(3),Q=1610.09 cal/g,P=37.31 GPa,D=9.12 km/s)have positive HOFs and remarkable insensitivity and good detonation performance,strongly suggesting them as the acceptable new-type explosive.The initiating power surpasses conventional primary explosives,such as HMX.The outstanding detonation power of compounds B and H contributes to its future prospects as a promising green primary explosive.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11264020 and 11364023)the Science Foundation of the Educational Committee of Jiangxi Province,China (Grant Nos.GJJ12463,11530,and 11540)+1 种基金the Doctoral Startup Fund of Jinggangshan University,China (Grant No.JZB11003)the Key Subject of Atomic and Molecular Physics in Jiangxi Province,China (Grant No.2011-2015)
文摘The structures and hydrogen storage properties of sodium atoms decorated B6 clusters are investigated by the B3LYP method with a 6-311＋G （d, p） basis set. For NamB6 （m = 1-3） clusters, Na atoms are always inclined to separate far enough from each other and not cluster together on a B6 cluster surface so that each Na atom has sufficient space to bind hydrogen molecules. The hydrogen storage gravimetric density of a two Na atoms decorated B6 cluster is 17.91 wt% with an adsorption energy per H2 molecule （AAE/H2） of 0.6851 kcal.mo1^-1. The appropriate AAE/H2 and preferable gravimetric density of the two Na atoms decorated B6 cluster complex indicate that it is feasible for hydrogen storage application in ambient conditions.
基金Project supported by the National Natural Science Foundation of China.
文摘Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with computer image analysis (CIA) and the transition of shear yielding zone (A_(sh)) with rubber volume fraction (V_f) was also manipulated. Results showed that the B-D transition of impact strength of blends corresponded to the fracture mechanism in PP/EPDM blends, from matrix crazing to matrix shear yielding. In addition, two new parameters, density of energy dissipation for crazing zone (F_(cz)) and for shear yielding zone (F_(sh)), are first obtained in this paper. The value of F_(sh) is about four times larger than that of F_(cz) for PP/EPDM blends, which confirmed that the matrix shear yielding is a more effective way of energy dissipation in blends.
基金supported by the projects of Chinese Academy of Sciences(Grant No.KZZD-EW-01-3)the National Basic Research Program of China(Grant No.2012CB825604)the National Natural Science Foundation of China(Grant Nos.41231065,41174137,41321003)
文摘Nighttime enhancements in ionospheric electron density at mid- and low-latitudes are investigated by using the critical frequency of the F2-1ayer （foF2） data measured from ionosonde stations at Okinawa （26.3°N, 127.8°E, Geomagnetic 15.3°N）, Yamagawa （31.2°N, 130.6°E, Geomagnetic 20.4°N）, Kokubunji （35.7°N, 139.5°E, Geomagnetic 25.5°N）, and Wakkanai （45.4°N, 141.7°E, Geomagnetic 35.4°N） in East Asia during several solar cycles. The results show that there are obvious seasonal and solar activity dependencies of the nighttime electron density enhancements. The enhancements are termed pre-midnight enhancement and post-midnight enhancement, according to the local time when the enhancement appeared. The former has a higher occurrence probability in summer months than in winter months. In contrast, the latter has a larger occurrence probability in winter months than in summer months. Moreover, the nighttime enhancements in electron density are more likely to occur at lower solar activity. These seasonal and solar activity variations of the nighttime enhancements in electron density can be explained in terms of the combined effects of downward plasma flux from the plasmasphere and the neutral winds.
