Shi De-Heng

Analytical Potential Energy Function, Spectroscopic Constants and Vibrational Levels for A1Σ+u State of Dimer 7Li2

The symmetry-adapted-cluster configuration-interaction method is used to investigate the spectroscopic properties of 7Li2(A1Σ+u) over the internuclear distance ranging from 2.4a0 to 37a0. The complete potential energy curves are calculated at numbers of basis sets. All the ab initio calculated points are fitted to the analytic Murrell–Sorbie function and then employed to compute the spectroscopic constants. By comparison, the spectroscopic constants reproduced by the potential attained at D95(3df,3pd) are found to be very close to the experiments, and the values (Te, De, Re, ωe, ωeχe, αe and Be) are of 1.732 93 eV, 1.161 36 eV, 0.313 27 nm, 251.95 cm−1, 1.623 cm−1, 0.005 35 cm−1, and 0.490 cm−1, respectively. With the potential obtained at D95(3df,3pd), the totally 75 vibrational states are found when J = 0. The vibrational levels, the classical turning points and the inertial rotation constants of the first 68 vibrational states are calculated for the first time and compared with the available measurements. Good agreement is obtained. The centrifugal distortion constants of the first 32 vibrational states are also reported for the first time. The reasonable dissociation limit for 7Li2(A1Σ+u) is deduced using the calculated results at present.

Accurate Analytic Potential Energy Function and Spectroscopic Study for G1Πg State of Dimer 7Li2

The reasonable dissociation limit for the G1Πg state of dimer 7Li2 is determined. The equilibrium internuclear distance, dissociation energy, harmonic frequency, vibrational zero energy, and adiabatic excitation energy are calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space in Gaussian03 program package at such numerous basis sets as 6-311++G, 6-311++G(2df,2pd), 6-311++G(2df,p), cc-PVTZ, 6-311++G(3df,3pd), CEP-121G, 6-311++G(2df,pd), 6-311++G(d,p),6-311G(3df,3pd), D95(3df,3pd), 6-311++G(3df,2p), 6-311++G(2df), 6-311++G(df,pd) D95V++, and DGDZVP. The complete potential energy curves are obtained at these sets over a wide internuclear distance range and have least squares fitted to Murrell–Sorbie function. The conclusion shows that the basis set 6-311++G(2df,p) is a most suitable one for the G1Πg state. At this basis set, the calculated spectroscopic constants Te, De, E0, Re, ωe, ωeχe, αe, and Be are of 3.9523 eV, 0.813 06 eV, 113.56 cm−1, 0.320 15 nm, 227.96 cm−1, 1.6928 cm−1, 0.004 436 cm−1, and 0.4689 cm−1, respectively, which are in good agreement with measurements whenever available. The total 50 vibrational levels and corresponding inertial rotation constants are for the first time calculated and compared with available RKR data. And good agreement with measurements is obtained.

First-principles calculation of elastic and thermodynamic properties of Ni2MnGa Heusler alloy

The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential (PW-PP) method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity Cv and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni2MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.

MRCI study of spectroscopic and molecular properties of X1Σ+g and A1Πu electronic states of the C2 radical

The potential energy curves (PECs) of X1Σ+g and A1Πu electronic states of the C2 radical have been studied using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in conjunction with the aug-cc-pV6Z basis set for internuclear separations from 0.08 nm to 1.66 nm. With these PECs of the C2 radical, the spectroscopic parameters of three isotopologues (12C2, 12C13C and 13C2) have been determined. Compared in detail with previous studies reported in the literature, excellent agreement has been found. The complete vibrational levels G(υ), inertial rotation constants Bυ and centrifugal distortion constants Dυ for the 12C2, 12C13C and 13C2 isotopologues have been calculated for the first time for the X1Σ+g and A1Πu electronic states when the rotational quantum number J equals zero. The results are in excellent agreement with previous experimental data in the literature, which shows that the presented molecular constants in this paper are reliable and accurate.The potential energy curves (PECs) of X1Σ+g and A1Πu electronic states of the C2 radical have been studied using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in conjunction with the aug-cc-pV6Z basis set for internuclear separations from 0.08 nm to 1.66 nm. With these PECs of the C2 radical, the spectroscopic parameters of three isotopologues (12C2, 12C13C and 13C2) have been determined. Compared in detail with previous studies reported in the literature, excellent agreement has been found. The complete vibrational levels G(υ), inertial rotation constants Bυ and centrifugal distortion constants Dυ for the 12C2, 12C13C and 13C2 isotopologues have been calculated for the first time for the X1Σ+g and A1Πu electronic states when the rotational quantum number J equals zero. The results are in excellent agreement with previous experimental data in the literature, which shows that the presented molecular constants in this paper are reliable and accurate.

Elastic collisions between Si and D atoms at low temperatures and accurate analytic potential energy function and molecular constants of the SiD(X2?) radical

Interaction potential of the OD（ X 2 Π ） radical is constructed by employing the CCSD（T） theory in combination with the correlationconsistent quintuple basis set, augccpV5Z, in the valence range. Using the potential, the spectroscopic parameters are accurately determined. The present D 0 , D e , R e , ω e , ω e χ e and B e values are of 44574, 46225 eV, 009702 nm, 2724923, 453534 and 100096 cm -1 , respectively, which are in excellent agreement with the recent measurements wherever available. A total of 23 vibrational states have been found when J = 0 by solving the radial Schrdinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which are in good agreement with the available experimental results. The total and various partialwave cross sections are calculated for the elastic collisions of O and D atoms in their ground states at low and ultralow temperatures when the two atoms approach each other along the OD（ X 2 Π ） potential energy curve. The impact energy range covers a vange from 10×10 -11 to 10 ×10 -3 a.u.. One shape resonance has been found in the total elastic cross sections. Contribution to the total elastic cross sections by each partial wave is investigated carefully. The results show that the shape of the total elastic cross sections is mainly dominated by the s partial wave. The shape resonances coming from the higher partial waves are covered up by the strong s partial wave cross sections.

Ab initio calculation on accurate analytic potential energy functions and harmonic frequencies of c3∑g+ and B1∏u states of dimer 7Li2

The comparison between single-point energy scanning (SPES) and geometry optimization (OPT) in determining the equilibrium geometries of c3∑g+ and B1∏u states of dimer 7Li2 is made at numerous basis sets by using a symmetry-adapted-cluster configuration-interaction (SAC-CI) method in the Gaussian 03 program package. In this paper the difference of the equilibrium geometries obtained by SPES and by OPT is reported. The results obtained by SPES are found to be more reasonable than those obtained by OPT in full active space at the present SAC-CI level of theory. And the conclusion is attained that the cc-PVTZ is a most suitable basis set for these states. The calculated dissociation energies and equilibrium geometries are 0.8818 eV and 0.3090 nm for c3∑g+ state, and 0.3668 eV and 0.2932 nm for B1∏u state respectively. The potential energy curves are calculated over a wide internuclear distance range from about 2.5a0 to 37a0 and have a least-squares fit into the Murrell-Sorbie function. According to the calculated analytic potential energy functions, the harmonic frequencies (ωe) and other spectroscopic data (ωeχe, Be and αe) are calculated. Comparison of the theoretical determinations at present work with the experiments and other theories clearly shows that the present work is the most complete effort and thus represents an improvement over previous theoretical results.

A Modified Potential Method for Electrons Scattering Total Cross Section Calculations on Several Molecules at 30∼5000 eV: CF4, CCl4, CFCl3, CF2Cl2, and CF3Cl

A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections (TCSs) for electrons scattering from several molecules (CF4, CCl4, CFCl3, CF2Cl2, and CF3Cl) over an incident energy range 30~5000 eV using the additivity rule model at Hartree–Fock level. The quantitative TCSs are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV. It is shown that the modified potential can successfully calculate the TCSs of electron-molecule scattering over a wide energy range, especially at lower energies.

Total cross sections for electron scattering at 10－5000eV by polyatomic molecules CF 4 , CF 3 H, C 2 F 4 , C 2 F 6 , and C 2 H 3 F 3

The additivity rule and complex optical potential approach have been employed to obtain the total (elastic and absorption) cross sections for electron scattering by molecules (CF4, CF3H, C2F4, C2F6 and C2H3F3) over an incident energy range from 10 to 5000 eV. Compared with other calculations and experimental data wherever available, excellent agreement has been obtained. Above 1000eV, there are no experimental data for CF3H, C2F4, C2F6 and C2H3F3, so the present results can provide comparison and predictions for experimental research.

Additivity rule for electron scattering on hydrocarbon molecules——considering two different shielding effects

Considering the overlapping among atoms in the molecule and the not full transparency of the molecule by electron, we propose a new formulation of the additivity rule (AR). Here the new AR is employed to calculate the total cross sections (TCS) for electron scattering on hydrocarbon molecules C2H2, C2H4, C2H6 and C3H8 over an incident energy range of 10–2000eV. The results are compared with the experimental data and other available theoretical calculations. This gives good agreement.

Elastic scattering of two ground-state N atoms

An interaction potential for an N2(X1σ+g) molecule is constructed by using the highly accurate valence internally contracted multireference configuration interaction method and the largest basis set, aug–cc–pV6Z, in the valence range. The potential is used to investigate the elastic scattering of two N atoms at energies from 1.0×10−11 to 1.0 × 10−4 a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and the shape of total elastic cross section curve is mainly dominated by the s-partial wave at very low collision energies. Three shape resonances are found in the total elastic cross sections. Concretely, the first one is very sharp and strong. It results from the g-partial-wave contribution and the resonant energy is 3.645 × 10−6 a.u. The second one is contributed by the h-partial wave and the resonant energy is 1.752 × 10−5 a.u. This resonance is broadened by those from the d- and f-partial waves. The third one comes from the l = 6 partial wave contribution and the resonant energy is 3.522 × 10−5 a.u. This resonance is broadened by those from the g- and h-partial waves. The N2(X1σ+g) molecular parameters, which are determined at the current theoretical level, achieve very high accuracy due to the employment of the largest correlation-consistent basis set in the valence range.