Ab Initio Calculation of Room Temperature Ionic Liquid 1-Ethyl-3-Methyl-Imidazolium and AlCl3

The Hartree-Fock method has been employed to investigate the electronic structures of EMIM＋（1- ethyl-3-methylimidazolium＋）, AlCl4^-, and EMIM＋-AlCl4^-. Full optimization and frequency analyses of EMIM＋, AlCl4^-, ten initial EMIM＋-AlCl4^- geometries have been carried out using the Gaussian-94 soft-package at 6- 31＋G（d,p） basis set level for hydrogen, carbon, nitrogen, chlorine, and aluminum atoms. The electronic structures of the lowest energy of EMIM＋-AlCl4^-pairs, single EMIM^＋, and AlCl4^- have been comparatively studied. The calculated results showed that the optimized EMIM^＋-AlCl4^-pair conformer of lowest energy was AlCl4^-outside the five-ring plane between methyl group and ethyl group with a H6--C122 distance of 2.7 A. The frequency analyses suggested that all stationary points were minimum points because of no imaginary frequency appearing, and the assigned frequencies were in agreement with experimental report. The interaction energy between EMIM^＋ and AlCl4^-was 776.2 kJ/mol.     

过渡元素电子组态的“反常”现象

本文用Hartree—Fock轨道能级分析了过渡元素电子组态的“反常”现象,提出在研究它们的电子组态时,应注意原子能态的高低,要把原子能态的高低作为决定电子组态的标准。     

Anisotropic Quantum Dots

This paper presents a detailed calculation of the electronic structure of quantum dots with various geometries. In particular, non-circular quantum dots are examined and their characteristic properties analysed. A general matrix method was developed that allows us to treat a wide range of quantum dots with arbitrarily complex confinement potentials. The Hartree-Fock self-consistent method is applied to study quantum dots with many-electrons.     

Theoretical Study on Adsorption of Methanol on Zeolite and Phosphorus Modified Zeolite

Methanol adsorption in zeolite and phosphorus modified zeolite has been investigated within the cluster model framework of quantum chemical calculation. Full optimization and frequency analysis of all cluster model have been carried out using Gaussian 94 soft package with Hartree-Fock method and B3LYP, B3P86 hybrid methods of density functional theory at 3-21G, 6-31G basis set level for hydrogen atoms and 6-31G (d) basis set level for the other atoms performed on small cluster model for CH3OH, H3Al(OH)SiH2(H2PO4), H3Al(OH)SiH2(H3SiO4), H3Al(OH-CH3OH)SiH2(H2PO4) and H3Al(OHCH3OH)SiH2(H3SiO4). The results show that phosphorus grafting in the zeolite framework has modified the chemical environment in the vicinity of the zeolite bridging hydroxyl. Phosphorus modification can enhance the acid strength of zeolite bridging hydroxyl, which was suggested by the lengthening of zeolite bridging hydroxyl O-H bond and the increasing methanol adsorption energy. This may be favorable to the initial CH3OCH3 formation in the methanol to gasoline (MTG) process.     

RDX中14N核四极耦合常数的Hartree-Fock计算

用Hartree-Fock方程计算得到RDX环上^14N的核四极作用的核四极耦合常数(用D95v2基组)分别为5．671，5．808，5．838MHz，非对称参数分别为0．545、0．560和0.564。从核四极共振实验获得的^14N核四极耦合常数分别为5．675、5．778，5．887MHz，非对称参数分别是0.6080、0．6380和0．6140。对环上三个氮原子的核四极耦合常数的理论值和实验值相差小而变化趋势存在显著差异的原因进行了讨论。     

Ab Initio Investigation of Methanthiol and Dimethyl Sulfide Adsorption on Zeolite

The Hartree-Fock and cluster model methods have been employed to investigate interactions of methanthiol or dimethyl sulfide on zeolites. Molecular complexes formed by adsorption of methanthiol on silanol H3SiOSi（OH）2OSiH3 with five coordination forms and dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with four coordination forms, and Bronsted acid sites of bridging hydroxyl H3Si（OH）Al（OH）2OSiH3 entering into interactions with methanthiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carded out using the Hartree-Fock method at 6-31＋G＊＊ basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms derived from methanthiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanthiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed that the nature of interactions leading to the formation of the bridging hydroxyl-methanthiol, silanol-methanthiol, bridging hydroxyl-dimethyl sulfide, silanol-dimethyl sulfide complexes was governed by the Van der Waals force as confirmed by a small change in geometric structures and properties. Methanthiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group as evidenced by the heat of adsorption, and the protonization of methanthiol adsorption on bridging hydroxyl model, which was supposed in the literature, was not found.     

Carbon particle phase stability as a function of size

The stability of particulate carbon formed in the detonation of high explosives has been investigated with first-principles and semiempirical molecular orbital calculations carried out on atomic clusters designed to represent the graphite and diamond phases. In order to compare the accuracy of different computational approximations, the dangling bonds were first capped with hydrogen atoms to maintain the sp2 or sp3 hybridization at the surface and then the surface contributions were removed by extrapolating the cohesive energies as a function of the cluster size. Calculations were also carried out on geometry optimized carbon clusters without capping atoms, resulting in reconstructed surfaces that may be a more realistic model for carbon formed under the extreme conditions of detonation. Comparison of the calculated heat of formation of graphite and diamond particles as a function of size predicts that the graphite phase becomes more stable for 104–105 carbon atoms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Accurate thermal conductivity coefficients for argon based on a state-of-the-art interatomic potential

An accurate interatomic potential was constructed by fitting a realistic function, constrained by theory, to a set of judiciously selected macroscopic and microscopic properties but not including thermal conductivity. Using this potential, accurate values of thermal conductivity of argon are obtained for the temperature range 100 to 6600 K. These are presented in tabular form as well as in terms of a correlation function.     

光气的太赫兹/红外吸收及拉曼散射振动光谱研究

采用Restricted Hartree-Fock(RHF)自洽场方法和密度泛函理论(DFT)方法对光气(COCl2)进行了RHF/6-31G、RHF/6-31+G、RHF/6-31++G、RHF/6-311G、RB3LYP/6-31G、RB3LYP/6-311G、RB3LYP/6-31+G、RB3LYP/6-31++...     

Theoretical investigation of interaction between psoralen and altretamine with stacked DNA base pairs

The present study is an attempt to have a better understanding of physicochemical interaction between anticancer drugs psoralen and altretamine with stacked DNA base pairs. The isolated structural parameters of the stacked base pairs were taken from the Protein Data Bank (PDB) of A-DNA file. The influence of the intercalators on the stability of stacked base pairs was studied based on the results of the interaction energies, which were calculated by the structures of intercalation complexes of psoralen and altretamine with stacked DNA base pairs. The higher dipole moment and polarizability which account for the dispersion forces play an important role during the intercalation of psoralen and altretamine molecules with the base pairs. The stability of the stacking base pairs and their interaction with the intercalator molecules due to the formation of hydrogen bond have been analyzed by Natural Bond Orbital analysis. It has also been noted that intercalator molecules produce significant changes in the values of the phase angle P of pseudorotation conformation of the sugar ring. The physicochemical properties of the psoralen and altretamine as well as the mechanism by which the drug interacts with DNA base pairs allow the rational design of novel anticancer drugs.