Ph. Durand

A nonempirical effective Hamiltonian technique for polymers: Application to polyacetylene and polydiacetylene

The recently proposed ab initio effective Hamiltonian technique is extended to polymer calculations and applied to various conformations of polyacetylene (all‐trans, cis‐transoid, and trans‐cisoid) and polydiacetylene (acetylenic and butatrienic backbones). Band structures, density of states (DOS), and XPS theoretical spectra are presented. Comparison of the band structures and DOS with those obtained by ab initio SCF (self‐consistent‐field) Hartree–Fock calculations of double zeta quality is excellent. The XPS theoretical spectrum for all‐trans polyacetylene is in good agreement with experiment. In polyacetylene, it is found that the π bands are quite similar for all three backbone conformations, though the σ bands differ significantly. For polydiacetylene, low ionization potentials are predicted—a few tenths of an eV larger than polyacetylene for the acetylenic backbone and a few tenths of an eV smaller than polyacetylene for the butatrienic backbone.

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...

Valence effective Hamiltonian study of the electronic structure of poly(p‐phenylene) and poly(p‐phenylene sulfide)

The parametrization of atomic potentials for sulfur is presented in the framework of the valence effective Hamiltonian (VEH) technique for polymers. The VEH method is applied to band structure and density of states calculations on poly(p‐phenylene) and poly(p‐phenylene sulfide), compounds of interest with regard to the conducting polymers area. The quality of the electronic structure description afforded by the VEH technique is demonstrated via a comparison of experimental XPS spectra for these polymers with spectra predicted theoretically. The ionization potential of poly(p‐phenylene sulfide) is predicted to be 0.7 eV higher than poly(p‐phenylene) in good agreement with experimental estimates.

A new general methodology for deriving effective Hamiltonians for atoms and molecules. Application to the transferability of atomic potentials in the hydrocarbon series

A new general methodology for deriving, from first principles, effective Hamiltonians by Fourier techniques is presented. The Fock operator is shown to be a particular one‐electron effective Hamiltonian. Other one‐electron effective Hamiltonians are suggested. The methodology is applied to a first study of the transferability of atomic potentials in the hydrocarbon series.

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.

Theory of Fano profiles

The theory of Fano profiles currently presented in the framework of scattering theory can also be investigated from model Hamiltonians projected in the basis of discrete states. It is shown that the wave operator approach of quantum dynamics applied to these models simultaneously provides the lineshapes and the dynamics of the quasi-bound states of interest. An analytical expression which generalizes Fano profiles is presented.

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.

Non-empirical pseudo-potentials for molecular calculations: III. Applications to transition metal compounds

Our non-empirical pseudo-potential method is tested on the molecules ScH3, TiH3F, MnO4 -, Zn(CH3)2 and Pd(CO)4. The calculations are performed with the PSIBMOL algorithm, described in paper I (Mole...

Theory of generalized Fano profiles

Standard Fano profiles can be described in terms of two interacting quasi-bound states. The theory of Fano profiles is extended to line profiles implying several interfering quasi-bound states. New analytical expressions of the lineshapes are derived. The concept of the shape polynomial is introduced which permits one to generalize the parameters of the Fano theory.

Capability of pseudopotential methods to simulate all-electron calculations with floating spherical gaussian orbitals

Abstract A pseudopotential method has been applied to the calculation of local molecular orbitals for the water molecule in its ground state. Calculated values of the bond length and of the bond angle are in good agreement with those obtained from analogous calculations involving all the electrons. Comparison with experimental data is of the same quality in the two types of calculations.