Yoshiko Sakai

Model potentials for molecular calculations. II. The spd‐MP set for transition metal atoms Sc through Hg

Model potential parameters and valence orbitals were generated for the transition metal atoms Sc through Hg. Only the nd and (n + 1)s valence electrons were treated explicitly and the effects of the remaining electrons were replaced by model potentials. For brevity they may be called sd‐MPs. Major relativistic effects were incorporated on the level of Cowan and Griffins quasirelativistic Hartree‐Fock (QRHF) method for the second and third transition metal atoms. The model potential parameters and valence orbitals were determined so as to reproduce the results of the numerical Hartree‐Fock reference calculations. The obtained valence orbitals have inner nodal structure. The model potential method can yield a balanced description of the s2dn–1, sdn, and dn + 1 configurations of the atoms. The polarization functions were also generated for the use in molecular calculations.

Model potentials for main group elements Li through Rn

Model potential (MP) parameters and valence basis sets were systematically determined for the main group elements Li through Rn. For alkali and alkaline-earth metal atoms, the outermost core (n−1)p electrons were treated explicitly together with the ns valence electrons. For the remaining atoms, only the valence ns and np electrons were treated explicitly. The major relativistic effects at the level of Cowan and Griffin’s quasi-relativistic Hartree–Fock method (QRHF) were incorporated in the MPs for all atoms heavier than Kr. The valence orbitals thus obtained have inner nodal structure. The reliability of the MP method was tested in calculations for X−, X, and X+ (X=Br, I, and At) at the SCF level and the results were compared with the corresponding values given by the numerical HF (or QRHF) calculations. Calculations that include electron correlation were done for X−, X, and X+ (X=Cl and Br) at the SDCI level and for As2 at the CASSCF and MRSDCI levels. These results were compared with those of all-elec...

Numerical Hartree–Fock energies of low‐lying excited states of neutral atoms with Z≤18

Numerical Hartree–Fock calculations have been performed for low‐lying excited states of the neutral atoms from He to Ar. Total energies, orbital energies, and the mean values of r of the outermost orbitals of each symmetry are tabulated as an aid to calibration of algebraic basis sets.

Extended Mulliken electron population analysis

The Mulliken electron population analysis has been a standard feature of computer output from the quantum mechanical molecular calculation. An extension of the original analysis is proposed here. It produces a point‐charge model of a molecule that retains the same electric dipole moment as calculated with the molecular wave function. The analysis offers visually more interesting information than the original Mulliken analysis. The extension can be made easily by extracting and printing out some additional numerical data usually once computed but discarded after being processed in molecular calculations.

Relativistic dsp-model core potentials for main group elements in the fourth, fifth and sixth row and their applications

Abstract We have developed advanced relativistic model core potentials (dsp-MCPs) for the fourth (Ga–Kr), fifth (In–Xe) and sixth-row (Tl–Rn) main-group elements, where the outermost core (n−1)d electrons were treated explicitly as well as the ns and np valence electrons. The remaining core electrons were replaced by dsp-MCPs. The major relativistic effects were incorporated into the dsp-MCPs at the level of Cowan and Griffins quasi-relativistic Hartree–Fock method. We applied dsp-MCPs to calculate spectroscopic constants for the ground states of the rare-gas diatomic molecules Kr2 and Xe2. The results obtained by coupled pair approximation using atomic natural orbital (ANO) basis sets, in which the correlation of inner (n−1)d electrons was included as well as those of the valence ns and np electrons, give excellent agreement with experimental values.

On the electron affinities of hexafluorides CrF6, MoF6, and WF6

The adiabatic electron affinities (EAs) of MF6 and MF−6 (M=Cr, Mo, and W) are calculated in a configuration interaction (CI) calculation using a model potential method. The calculated EA of 3.85 eV for WF6 agrees well with the observed values. The difference (1.52 eV) between the calculated EA of MoF6 and that of WF6 shows also a very good agreement with the experimental ones. CrF6 has a very high EA of 8.24 eV. The CrF−6 anion has positive EA and the CrF2−6 dianion is thus most stable in the CrFq−6 (q=0, 1, and 2) sequence, while WF−6 does not have a positive EA. The EAs of MF6 calculated by CI calculations are smaller than those by SCF calculations. This negative correlation effect on the AEs is also discussed.

Theoretical study of low-lying electronic states of TiCl and ZrCl

Low-lying electronic states of TiCl and ZrCl were investigated by the complete active space SCF (CASSCF), multi-reference singly and doubly excited configuration interaction (MRSDCI), and multi-reference coupled pair approximation (MRCPA) calculations using the model core potential (MCP) method. Relativistic effects were incorporated in the MCP and basis sets for Zr at the level of Cowan and Griffin’s quasi-relativistic Hartree–Fock method. The 4Φ state was found to be the ground state of TiCl, whereas the 2Δ state was the ground state of ZrCl at all levels of calculation. Two low-lying excited states were very close in energy to the ground state. The excited 4Σ− and 2Δ states of TiCl were higher than the ground state by 0.102 eV and 0.458 eV, respectively, and the excited 4Φ and 4Σ− states of ZrCl were higher by 0.094 eV and 0.110 eV, respectively, at the MRCPA level. The calculated values of re(2.319 A) and ωe(382 cm−1) for the ground 4Φ state of TiCl are quite close to the values of re(2.351 A) and ωe(...

Model calculation for the frequency shift in CO coadsorbed with K on Cu(001)

The dramatic frequency shift recently observed for CO coadsorbed with alkali atoms on transition metals is analyzed by calculating the electronic structure of Cu12K2CO and by comparing it with that of Cu12CO, K2CO, CO−, and CO at the self-consistent Hartree-Fock model-potential level. The CO vibrational frequency in the coadsorbed system is reproduced by the calculation, and the frequency shift is elucidated: it is brought about by electron redistribution which leads to reduction of the overlap population between the C and O. The electron redistribution is caused mainly by an increase of electron flow into the 2π level due to a downward shift of this level because of direct interaction between CO and K.

Ab initio CASSCF and MRSDCI calculations of the (C6H6)2+ radical

Abstract Ab initio complete-active-space self-consistent-field (CASSCF), single-reference singly and doubly excited configuration interaction (SRSDCI), and multi-reference SDCI (MRSDCI) calculations were performed for the benzene trimer cation, (C 6 H 6 ) 3 + , in its ground state. We found that the global minimum of the cation is the distorted C 2v sandwich structure, which is 0.032 eV lower than the D 6h sandwich structure. The dissociation energy ( D e ) relative to (C 6 H 6 ) 2 + +C 6 H 6 was calculated to be 0.43 eV, in comparison to the experimental value ( D 0 ) of 0.34±0.02 eV. Our calculations revealed that most of the charge of the trimer cation is localized in the central benzene ring, whose gross charge is +0.9. The low-lying excited states arising from the π–π transition are also discussed.

Hole-burning spectroscopy and ab initio calculations for the aniline dimer

Abstract The mass-resolved spectrum indicates that only one conformation contributes to sharp peaks observed in the S 1 ←S 0 resonance two-photon ionization (R2PI) spectrum. However, geometry optimizations at the MP2/cc-pVDZ level suggest that two conformational isomers are stable: a head-to-head conformation with a single NH⋯N hydrogen bond and a head-to-tail conformation with double NH 2 ⋯π hydrogen bonds. The calculations show that the head-to-tail conformation is more stable by 1.18 kcal mol −1 .