Ab initio potential energy surface and anharmonic vibration spectrum of NF_(3)^(+)

Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction(VCI). Based on an iterative algorithm, the surfaces(SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q_(6) symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF_(3)^(+) are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra.Modal antisymmetric stretching ν_(5) and symmetric stretching ν_(6) exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory.

Elastic constants of Al and TiN calculated by ab initio method

The elastic constants of Al single crystal were calculated by ab initio method for calibration. Three deformation directions were selected in order to obtain the different constants of c 11 , c 12 and c 44 . The cohesion energy curves of the three deformation directions were calculated. The results of the second order partial differential at the equilibrium point of the cohesion energy curve provide the elastic constants of the Al single crystal. The changes of crystal symmetry and lattice can lead to the deviations of the calculated cohesion energy curves and the accurate elastic constants can not be obtained, but when the correction is taken into calculation, the calculated results are very close to the literature data. It is very difficult to obtain the elastic constants of thin films by experiment and the data from the handbook are scattered in a large scale. However, the elastic constants calculated by this method can be served as a standard. Though the errors of TiN elastic constants calculated by this method are a little higher than that for Al, the results are acceptable. [

A NEW AB INITIO CALCULATION METHOD OF INNER-SPHERE REORGANIZATION ENERGY

On the basis of the-improved self-exchange model of reorganization phenomenon and accurate potential functions from ab initio calculation at HFSCF 6-31G* and DZP levels a new calculation method was,presented for the inner-sphere reorganization energy, values for diatomic molecular redox couples in gas phase electron transfer process have been calculated. Results agree well with the experimental data, and the effectiveness and importance of this method have been demonstrated for calculation of inner-sphere reorganization energy in gas phase electron transfer process.

Elastic and Optoelectronic Properties of KCdF3:ab initio Calculations through LDA/GGA/TB-mBJ within FP-LAPW Method

Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per- ovskite KCdF3. Tile Kohn Sham equations are solved by applying the full potential linearized augmented plane wave （FP-LAPW） method. The exchange correlation effects are included through the local density approximation （LDA ）, generalized gradient approximation （GGA） and modified Becke-Johnson （mBJ） exchange potential The calculated lattice constant is in good agreement with the experimental result. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young＇s modulus and Poisson＇s ratio are calculated. KCdF3 is ductile and elastically anisotropic. The calculations of the electronic band structure, density of states （DOS） and charge density show that this compound has an indirect energy band gap （M-F） with a mixed ionic and covalent bonding. The contribution of the different bands is analyzed from the total and partial density of states curves. Optical response of the dielectric functions, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of O-40eV. The compound KCdF3 can be used for high-frequency optical and optoelectronic devices.

Synthesis,Crystal Structure and Quantum Chemistry of Dibutyltin 3,4-Dimethoxybenzotate Compound

The dibutyltin 3,4-dimethoxybenzotate compound {[（3,4-（CH3O）2C6H3COO） Sn（Bu-n）2]2O}2 has been synthesized by the reaction of dibutyltin oxide with 3,4-dimethoxybenzoic acid. Its structure was determined by X-ray single-crystal diffraction. The crystal belongs to the triclinic system,space group P1 with a = 1.2003（2）,b = 1.2821（3）,c = 1.3666（3） nm,α = 80.50（3）,β = 65.56（3）,γ = 73.36（3）°,Z = 2,V = 1.8318（6） nm3,Dc = 1.530 Mg·m-3,μ（MoKa） = 1.413 mm-1,F（000） = 860,R = 0.0554 and wR = 0.1092. In the complex,each tin atom adopts a distorted tigonal bipyramidal structure,and the dimer structure is shaped by one Sn2O2 planar four-membered ring. The stabilities of the title complex,along with its orbital energies and composition characteristics of some frontier molecular orbitals have been investigated by means of quantum chemistry calculation methods.

Ab Initio MO Studies on the Reaction Mechanism for Carbonyl Insertion Catalyzed by Carbonyl Cobalt Complex

Ab initio method, under the effective core potential(ECP) approximation at HF/LANL2DZ level, has been employed to study the reaction mechanism of the carbonyl insertion of olefin hydroformylation catalyzed by a carbonyl cobalt HCo(CO)_3. The two reaction paths have been discussed. The calculated potential energy barriers for the carbonyl migration and the ethyl group migration are 105. 0 kJ/mol and 39. 17 kJ/mol, respectively. The results indicate that the reaction path via ethyl migration is more energetically favorable than that via carbonyl insertion.

Structure and bonding properties of Y doped Σ37 grain boundary in alumina

The microscopic structures and the bonding properties of Y-doped and undoped （011^-8）/[044^-1]/180° （∑37） grain boundaries in alumina are investigated by using ab initio method. The formation energy of grain boundary and the segregation energy of Y to grain boundary are acquired. Electronic structures, potential distributions, bond orders and effective charges of Y-doped and undoped ∑37 GB systems are calculated. Our results reveal that the higher strength Y-O bond than Al-O bond is ascribed to the hybridization of Y（4p, 3d） with O（2s）. Meanwhile, dopant Y also causes a change in potential distribution in the grain boundary region, thereby further affecting the transport property of ceramic alumina.

Synthesis,Crystal Structure and Quantum Chemistry of a Hydration Dibenzyltin Dichloride

A novel organotin hydration dibenzyltin dichloride has been synthesized and its crystal structure was determined by X-ray diffraction. The crystal belongs to monoclinic, space group Pc with a = 1.1918（5）, b = 0.6199（2）, c = 1.1074（5）nm, β = 106.899（7）°, V= 0.7828（8）nm3, Z = 2, Dc = 1.654 g/cm3,μ（MoKa） = 19.59 cm^-1, F（000） = 384, R = 0.0564 and RwR = 0.1427. The Sn-C bonds are 0.2140（9） and 0.2152（5） nm, Sn-Cl are 0.2385（4） and 0.2497（3） nm, and Sn-O is 0.2388（7） nm. The tin atom is five-coordinated in a distorted trigonal bipyramidal configuration. The study on the title complex has been performed with quantum chemistry calculation by means of G98W package on the Lanl2dz basis set. The stability of the complex as well as the orbital energies and composition characteristics of some frontier molecular orbitals has been investigated.

Investigation of the topological shape of bovine serum albumin in solution by small-angle x-ray scattering at Beijing synchrotron radiation facility

This paper reports that at a newly constructed small-angle x-ray scattering station of Beijing Synchrotron Radia- tion Facility, the topological shape of ligand-free bovine serum albumin in solution has been investigated. An appropriate scattering curve is obtained and the calculated value of the gyration radius is 31.2~=t=0.25 ~_ （11=0.1 nm） which is co- incident with other ones＇ results. It finds that the low-resolution structure models obtained by making use of ab initio reconstruction methods are fitting the crystal structure of human serum albumin very well. All of these results perform the potential of the beamline to apply to structural biology studies. The characteristics, the defects, and the improving measures of the station in future are also discussed.

Ab initio investigation of the mechanical properties of copper

Employing the ab initio total energy method based on the density functional theory with the generalized gradient approximation, we have systematically investigated the theoretical mechanical properties of copper （Cu）. The theoretical tensile strengths are calculated to be 25.3 GPa, 5.9 GPa, and 37.6 GPa for the fcc Cu single crystal in the [001], [110], and [111] directions, respectively. Among the three directions, the [110] direction is the weakest one due to the occurrence of structure transition at the lower strain and the weakest interaction of atoms between the （110） planes, while the [111] direction is the strongest direction because of the strongest interaction of atoms between the （111） planes. In terms of the elastic constants of Cu single crystal, we also estimate some mechanical quantities of polycrystalline Cu, including bulk modulus B, shear modulus G, Young＇s modulus Ep, and Poisson＇s ratio ~.

An ab-initio study of a^1B_(3u)→X^1A_g transition in a neutral molecular N_2 dimer

Presents the ab initio calculations performed for different symmetry groups of neutral molecular N 2 dimer, and the calculation of ground state and low lying singlet excited states for each symmetry group and concludes from the results that there is an electric dipole transition between X 1A g and a 1B 3u (singlet singlet) excited states belonging to D 2h group symmetry, and discusses the vibrational energy levels and emission spectra calculates for this transition.

A Theoretical Study on the Hydrogen-bonded Dimers of HNCO Molecules

Ab initio method has been employed to investigate the hydrogenbond between two HNCO molecules. Two types of hydrogen-bondings in HNCO dimers have been found, one type is N-H…O, the other is N-H…N. The latter is a little stabler than that of the former. The stabilization energies of the two types of dimers are estimated to be 13KJ/mol-21KJ/mol.

The Electronic Structures of Dimeric Diboroxane and Aldiminoborane

e have studied the electronic structures of dimeric diboroxane and aldiminob-orane by nieans of STO-3G .ib iuitio SCF method. The energies and the componentanalysis of niolecular orbitals near to frontier orbital have been given. By bothKoopman' s theoreni and △E_(scf)mietliod we have calculated the ionization potentialsof 8 higlier occupied orbitals and discussed the electron relaxation effect on IP' s cal-culations and the charge distribuuons for the two molecules.

A charge-conserving approximation——method for ab initio calculations

A new method is presented for approximate ab initio calculations in quantum chemistry. It is called CCAM (charge conserving approximation method). The calculation method does not include the use of empirical parameters. We use Slater type orbitals as basis set, replacing STO's by STO-2G functions to evaluate three- and four-center integrals and making the STO-2G two- orbital charge distributions have the same total charge as STO. The results are presented for test calculations on five molecules. In view of these results, CCAM is better than ab initio calculations over STO-6G in the results on total energies, kinetic energies and occupied orbital energies. In atomic populations, dipole moments and unoccupied orbital energies, CCAM is also satisfactory. We estimate that CCAM would be as fast as ab initio calculations over STO-2G in evaluating molecular integrals.

Methylation of 5-Amino-3-methylthio-1 H-pyrazole Derivatives and Two Related Crystal Structures

5-Amino-3-methylthio-1H-pyrazoles are very important building blocks from which a wide variety of pyrazole de-rivatives can be prepared. When substituted 5-amino-3-methylthio-1H-pyrazole was treated with CH3I, the methy-lation occurres at endocyclic two nitrogens at the same time. The ratio of isomers in products was depended upon the nature of 4-position substituent in the pyrazole ring. The products were characterized by X-ray diffraction analysis, and the ratios of isomer were explained by means of the results of ab inito calculation.

Effect of tensor correlations on the depletion of nuclear Fermi sea within the extended BHF approach

We have investigated the effect of tensor correlations on the depletion of the nuclear Fermi sea in symmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach by adopting the AV 18 two-body interaction and a microscopic three-body force.The contributions from various partial wave channels including the isospin-singlet T = 0 channel,the isospin-triplet T = 1 channel and the T = 0 tensor 3SD1 channel have been calculated.The T =0 neutron-proton correlations play a dominant role in causing the depletion of nuclear Fermi sea.The T =0 correlation-induced depletion turns out to stem almost completely from the 3SD1 tensor channel.The isospin-singlet T = 0 3SD1 tensor correlations are shown to be responsible for most of the depletion,which amounts to more than 70 percent of the total depletion in the density region considered.The three-body force turns out to lead to an enhancement of the depletion at high densities well above the empirical saturation density and its effect increases as a function of density.

Theoretical study on tetrazole and its derivatives (3) MP2 and thermodynamic calculations of amino derivatives of tetrazole

Fully optimized geometries and electronic structures of amino derivatives of tetrazole are obtained at MP2/6-31G* level. The tetrazole rings are planar and aromatic for all the amino derivatives of tetrazole. The amino group is not co-planar with the ring and its conformation is mainly determined by the lone pair electronic repulsion between the substituents and the ring. N(4) atom is more negatively charged and is the most probable coordination site. The energy gaps between LUMOs and HOMOs of 2H-aminotetrazoles and C-aminotetrazole neutrals are smaller than those of the corresponding 1H-isomers and N-aminotetrazole neutrals respectively. The IR frequencies, thermodynamic properties and temperature-dependent functions for heat capacities in the fom (a + bT + cT2) in the 300–1000K range are reported.

Density functional theory (DFT) and ab initio investigations of the electronic and molecular structures of the monomer and the dimer of trimethylaluminium

The electronic and molecular structures of the monomer and dimer of trimethylaluminium have been studied using density functional theory and ab initio MP2 method. The optimized geometry of the monomer Al(CH3)3 is of C3h symmetry, whew that of the dimer [Al(CH3)3]2 contains a carbon-bridged four-membered ring structure with C2h symmetry. The hydrogen-bridged six-membered ring structure is found to be unstable. The calculated dimerization energy for the four-membered ring structure is 78 kJ/mol, in close proximity to the experimental due of 85.27 kJ/mol.