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ab initio and density functional theory studies of the structure,gas-phase acidity and aromaticity of tetraselenosquaric acid

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Chinese Journal of Chemistry 2000年第6期18卷 808-814页

作者：周立新 Department of Chemistry Fuzhou UniversityFuzhouFujian 350002 China

Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure, acidity (free energy of deprotonation, ΔG*) and aromaticity of tetraselenosquaric acid (3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2 C4 Se4)are reported. The global minimum found on the potential energy surface of tetraselenosquaric acid presents a planar conformation. The ZZ isomer was found to have the lowest energy among the three planar conformers and the ZZ and ZE isomers are very dose in energy. The optimized geometric parameters exhibit a bond length equalization relative to reference compounds, cyclobutanediselenone, and cyclobutanediselenol. The computed aromatic stabilization energy (ASE) by homodesmotic reaction is -77.4 (MP2(fu)/6–311+G** /RHF/6 - 311 + G** ) and - 54.8 kJ/mol (B3LYP/6 - 311 + G** //B3LYP/6 -311 + G**). The aromaticity of tetraselenosquaric acid is indicated by the calculated diamagnetic susceptibility exaltation (A) -19.13 (CSGT(IGAIM)-RHF/6–311 + G**// RHF/6–311 + G** and -32.91 (4π·10?6 m?3/mol)(CSGT(I-GAIM)-B3LYP/6 - 311 + G* * //B3LYP/6 - 311 + G**). Thus, tetraselenosquaric acid fulfils the geometric, energetic and magnetic criteria of aromaticity. The calculated gas-phase acidity is ΔG1*(298k) = 1257.7 and ΔG*2 (298k) = 1617.1 kJ/mol. Hence, tetraselenosquaric acid is the strongest acid among the three squaric acids (3, 4-dihydroxy-3-cyclobutene-1, 2-dione, H2 C4 3,4-dithiohydroxy-3-cyclobutene-1,2-dithione, H2C4 S4, 3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2C4Se4).

关键词： Tetraselenosquaric acid ab initio density functional theory (DFT) gas-phase acidity aromaticity

ab initio calculations of mirror energy difference in sd-shell nuclei

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Chinese Physics C 2023年第12期47卷 73-95页

作者：李红蕙李健国谢萌冉左维 Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

Mirror energy difference is a key observable in isospin symmetry breaking,containing rich information about nuclear *** the mechanisms underlying mirror energy difference is important in nuclear *** the present work,we extensively investigated mirror energy difference using ab initio valence-space inmedium similarity renormalization group approach,focusing specifically on sd-shell *** low-lying spectra of Al isotopes and N=8 isotones,together with their mirror nuclei,were calculated,followed by a systematic analysis of the evolution of the mirror energy *** results suggest that the large mirror energy difference is mainly caused by the weakly-bound effects and large average occupations of the 1s1/2 ***,we compare the results of our ab initio calculations with shell model results,elucidating the relationship and coherence between these two models.

关键词： ab initio isospin symmetry breaking Thomas Erhman shift

An ab initio Theoretical Study on the Nonadiabatic Coupling for Na+I_2 Collision System

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Chinese Journal of Chemistry 2003年第6期21卷 617-620页

作者：孙孝敏蔡政亭冯大诚 Institute of Theoretical Chemistry Shandong University Jinan Shandong 250100 China

The ionic and neutral state potential energy surfaces (PESs) of Na+I 2 collision system have been calculated on QCISD(T) level by using ab initio method. The location and depth of the potential well, the collision radius and their fine structures have been analyzed at the equilibrium geometry of I 2 molecule. The electronic transfer probabilities are also calculated in terms of Landau Zener model. The lifetime of scattering resonance state is evaluated by the uncertainty principle. All the results have been compared with those obtained according to the Aten Lanting Los PES and Feng's PES.

关键词： ab initio ion pair formation process potential energy surface nonadiabatic coupling scattering resonance state

ab initio Calculations on Halogen Bond Between N—Br and Electron-donating Groups

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Chemical Research in Chinese Universities 2007年第3期23卷 355-359页

作者： WANG Yan-hua CHEN Xue-song ZOU Jian-wei YU Qing-sen College of Biology and Environment Engineering Zhejiang Shuren University Hangzhou 310015P. R. China Key Laboratory for Molecular Design and Nutrition Engineering of Ningbo City Ningbo Institute of Technology Zhejiang University Ningbo 315100 P. R. China Department of Chemistry Zhejiang University Hangzhou 310027 P. R. China

ab initio calculations of complexes formed between N-bromosuccinimide and a series of electron-donating groups were performed at the level of MP2/Lanl2DZ^＊ to gain a deeper insight into the nature of the N--Br halogen bonding. For the small complexes, H3 C--Br… NH3 and H2 N--Br…NH3 , the primary calculation has demonstrated that the N--Br in H2 N--Br… NH3 can form a much stronger halogen-bonding complex than the C--Br. A comparison of neutral hydrogen bond complex series reveals that the electron-donating capacities of the atoms decrease in the order, N 〉 O 〉 S; 0 （ sp^3 ）〉 0 （ sp^2 ）, which is adequate for the C--Br halogen bonding. Interaction energies, in conjunction with the geometrical parameters show that the affinitive capacity of trihalide anions X^-3 with N-bromosuccinimide are markedly lower than that of the corresponding X^- with N-bromosuccinimide, even lower than those of neutral molecules with N-bromosueeinimide. AIM analyses further eorffirmed the above results.

关键词： Halogen bond N-bromosuccinimide ab initio AIM theory Interaction energy

ab initio Study on The Influence of Spin State upon Bonding and Interaction in FeCO*

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Chemical Research in Chinese Universities 1999年第2期15卷 71-81页

作者： XU Xin L Xin XIAN Hui CAI Yu WANG Nanqin ZHANG Qianer State Key Laboratory for Physical Chemistry of Solid Surface Institute of Physical ChemistryDepartment of ChemistryXiamen UniversityXiamen361005

Four FeCO states with 3d4s and 3d3d electrons spinpaired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding and interaction in *** calculation results show that the FeCO bonding and interaction are determined by a balance between the bonding stabilization and the exchange stabilization with 3d4s electron spinpairing or without *** 3d3d electron spinpairing versus unpairing has a surprised effect on the FeCO bonding properties even though the 3d orbitals are usually considered as non bonding ones.

关键词： ab initio Carbon monoxide Iron Transitionmetal carbonyl Bonding mechanism

ab initio Study on Enantioselective Reduction of Ketones Catalyzed by Thiazolidino[3,4-c]oxazaborolidines

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Chinese Journal of Chemistry 2002年第10期20卷 983-989页

作者：李明谢如刚田安民 DepartmentofChemistry SichuanUniversityChengduSichuan610064china DepartmentofChemistry SouthwestNormalUniversityChongqing400715china

The ab initio molecular orbital method is employed to study the enantioselective reduction of acetophenone with borane catalyzed by thiazolidinooxazaborolidine. Computation result shows that the controlling step for the reduction is the decomposition of the catalyst-alkoxyborane adduct and the reduction leads to S-alcohols. The transition state of the hydride transfer from the borane moiety to the carbonyl carbon of acetophenone is a twisted chair structure with a B(2)-N(3)-B BH 3-H BH 3-C CO-O CO 6-membered ring.

关键词： ab initio thiazolidinooxazaborolidine enantioselective reduction of acetophenone transition state

ab initio Investigation of Decomposition of HCF_2OH

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Chemical Research in Chinese Universities 1999年第1期15卷 89-91页

作者： HOU Hua GUO Jing-zhong LIU Chuan-pu GU Yue-shu DENG Cong-hao Department of Chemistry Shandong UniversityJinan250100

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关键词： ab initio Dissociation Reaction mechanism

ab initio study on mechanisms of singlet oxygen reaction with ethylene

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Chinese Journal of Chemistry 1994年第1期12卷 26-32页

作者： CHEN, De-Zhao CHEN, Bao-Ji NING, Shi-GuangDepartment of Chemistry , Shandong Teachers’ University, Jinan, Shandong 250014, China Department of Chemistry Shandong Teachers' University Jinan Shandong 250014 China

The reaction of singlet oxygen with ethylene has been studied at the ab initio level with both HF/3-21G and HF/6-31G basis sets, fully optimizing the geometries of the critical points. The transition state leading to the intermediate peroxirane from the initial reactants is found,Iocated at 81.71 kJ/mol above the dissociation limit. The vibrational analysis is done with two basis sets. From the results it can be seen that the frequencies have not been made an improvement obviously with augmented 6-31G compared to 3-21G basis; it follows that main reason for too high HF/3-21G frequency could mainly be the vibrational anharmonicity. The eigenvector corresponding to the single imaginary vibrational frequency is dominated by the larger O-O distance. The finding of the transition state confirms that the peroxirane minimum can be reachable passing through a peroxirane-like saddle point. In addition , the mechanisms of the reaction forming oxirane are discussed as well.

关键词： ab initio singlet oxygen ethylene peroxirane oxirane.

ab initio Study of Hyperconjugative Effect on Electronic Wavefunctions of 2-chloroethanol

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Chinese Journal of Chemical Physics 2011年第4期24卷 434-438,I0004页

作者：王克栋张海霞刘玉芳河南师范大学物理与信息工程学院新乡453007 河南师范大学数学与信息科学学院新乡453007

The electronic structure of five conformers of 2-chloroethanol was studied by ab initio calculations at B3LYP and MP2 levels of theory with aug-cc-pVTZ basis set. The existing hydrogen bond and hyperconjugation effects on the stability of 2-chloroethanol conformers were discussed on the base of natural bond orbital analyses. The result exhibits that hyperconjugation is the main factor to determine the stability of conformers. Such effects on the electron wavefunctions of the highest-occupied molecular orbital （HOMO） of different conformers are demonstrated with electron momentum spectroscopy, exhibiting the obviously different symmetries of the HOMO wavefunctions in momentum space.

关键词： ab initio Hydrogen bond Natural bond orbital Hyperconjugative effect Momentum distribution