Jean-Claude Barthelat

A theoretical method to determine atomic pseudopotentials for electronic structure calculations of molecules and solids

The characteristic features of model potentials, effective potentials and pseudopotentials are carefully investigated. Then we justify our choice to work only with hermitian pseudopotential operators, and we develop a general non-empirical method to determine atomic pseudopotentials. In view of their numerical use for molecular calculations, these pseudopotentials are cast into semi-local forms, and their parameters are obtained by a least-squares process; tables of parameter values are given for the two first rows of the periodic system.

Non-empirical pseudopotentials for molecular calculations

Improved three-parameter atomic pseudopotentials are theoretically determined from lithium to krypton. In view of further molecular calculations, accurate expressions are given for the pseudopotent...

Extended gaussian-type valence basis sets for calculations involving non-empirical core pseudopotentials

Revised values of core pseudopotential parameters are presented together with optimized PS-31 G valence basis sets for atoms from Li to Ca and from Ga to Kr. Studies with more than thirty test molecules indicate a very good agreement with 6–31 G results for atomization energies, geometries, dipole moments and force constants.

New atomic pseudopotentials for electronic structure calculations of molecules and solids

Abstract A systematic non-empirical method is developed to determine atomic pseudopotentials; their parameters are calculated by means of a least-squares process. The efficiency of such a method appears clearly in the calculation of the valence molecular orbitals of the silane molecule.

Non-empirical pseudopotentials for molecular calculations: II. Basis set extension and correlation effects on the X2 molecules (X=F, Cl, Br, I)

The ability of the atomic pseudopotential proposed in Part I to reproduce the all-electron basis set extension and correlation effects in molecules has been tested on F2 and Cl2 through systematic ...

Copper atom as a one‐electron system: Theoretical study of Cu2 and CuH

The ground state characteristics of Cu2 and CuH have been calculated by using explicitly only one electron for each copper atom. The remaining 28 electrons are kept as a frozen core, employing a nonempirical pseudopotential. A recently proposed perturbation method for core‐valence polarization and correlation effects has been used to study, these molecules. The results are in fairly good agreement with the experimental values. Study of copper clusters with this method is suggested.

Decisive role of π conjugation in the central bond length shortening of butadiene

Abstract The influence of π conjugation and hyperconjugation in the shortening of the central C-C bond in butadiene with respect to a Csp3-Csp3 bond in alkanes is theoretically investigated by a direct analysis. As expected from simple π models it is demonstrated that the origin of this shortening is mainly due to π conjugation in the planar s-trans conformation while hyperconjugation largely compensates the lack of π conjugation in the perpendicular form and leads to a similar shortening of the central bond, These results contradict one of the conclusions of a recent ab initio study.

Theoretical study of the electronic structure of the BaH molecule

The electronic structure of BaH is investigated using a 10‐electron relativistic pseudopotential on Ba, frozen core configuration interaction (CI) with three active electrons and core‐polarization potential. Fine structure is taken into account with a semiempirical spin–orbit operator. The electronic properties of all states dissociating into Ba(6s2,6s15d1,6s16p1) +H(1s) are obtained and generally found in agreement with experiment within 0.03 A for equilibrium distances, 300 cm−1 for transition energies, 30 cm−1 for vibrational frequencies, except for the D 2Σ+ state. The methodology used in this work is discussed in the light of the results presented here.

Pseudopotentials and localized molecular orbitals. Application to the methane molecule

Abstract A pseudopotential method is used for the calculation of the localized molecular orbitals of the ground state of the methane molecule. Good agreement with calculations involving all the electrons and with experiment is obtained.

Stabilization of a π double bond between two boron atoms: A theoretical approach

Abstract The low-lying states of HBBH, HBBNH 2 and H 2 NBBNH 2 are investigated by means of ab initio CI calculations using a double-zeta + polarization basis set. Diborene is found to have a 3 ∑ g − ground state. Replacement of hydrogen by amino groups on each side of the BB bond leads to an ethylene-like bond which corresponds to a 1 A g state of D 2h symmetry. π back-donation by the amino lone pairs is responsible for the stabilization of this state.