A. Ažman

On the electronic structure of polydiacetylenes as studied by the ab initio crystal orbital method

Abstract Ab initio “exact” exchange Hartree-Fock crystal orbital energy band structure calculations have been done for six polydiacetylene (PDA) models. The effect of fluorine substitution on the gap, stability and transport properties is small. The stability of the three configurations considered is in accord with experiments. The obtained forbidden band gaps are larger than the experimental one. Charge carrier mobility, mean free path and pre-exponential factor of conductivity are estimated by the deformation potential approximation. These values are compatible with the classical band type conduction mechanism for PDA.

Ab initio crystal orbital treatment of hydrogen fluoride (HF) chains

Abstract Ab initio LCAO Hartree-Fock crystal orbital calculations are reported for hydrogen fluoride (HF) chains with symmetrical and asymmetrical position of the H atoms in the hydrogen bonds. An extra binding energy for the infinite chain is obtained in comparison with small clusters. The energy band structures obtained with the different geometrical arrangements are discussed.

AB initio energy band structure of polysulfur nitride, (SN)x

Abstract All electron energy band structure is reported for an infinite one-dimensional model of polysulfur nitride, (SN) x , using the ab initio LCAO Hartree-Fock method. The calculated values of the effective mass and density of states at the Fermi level are −0.72 m e and 0.06 states/(eV spin molecule), respectively. An appreciable amount of charge transfer (0.30 e ) from sulfur to nitrogen was obtained. Finally, comparison is made with the results of a semi-empirical version of the same method.

The numerical solution of the BGYB equation for the liquid interacting with the rigid wall

The density profile at the crystal-liquid interface is calculated with the help of the Born-Green-Yvon-Bogolyubov integrodifferential equation. It was found that meaningful solution can be obtained after adapting the temperature and replacing the crystalline bulk by a rigid wall.

Ab initio crystal orbital studies on linear chains of H atoms

Anab initio crystal orbital method is used to calculate the energies of an infinite chain of H atoms and of linear arrangements of H2 molecules with different interatomic distances. The H2 arrangements are not stable in respect to isolated molecules. The cohesive energy of an optimized arrangement of H atoms chain is 0.0354 a.u.

Ab initio calculation of magnetic shielding with a finite perturbation method

Abstract Fluorine and proton magnetic shieldings of HF are calculated with the use of an ab initio finite perturbation molecular orbital theory with four different basis sets of gauge invariant atomic orbitals.

Crystal orbital studies of the (HCN)x chain

Abstract Restricted and unrestricted Hartree—Fock methods are applied to study the alternating and the non-alternating structure of (HCN) x .

Experimental and semi-theoretical investigations of O, S, and Se-amides and ureas.: I. The electronic configurations

Abstract Huckel M.O. calculations have been made on acetamide and several selenoamides and Pariser-Parr-Pople calculations on urea, thiourea, and selenourea. The results are compared mainly to force constants and 14 N Chemical shifts to show the trends in structure of amide groups if oxygen is replaced by sulphur and selenium, respectively. Electronic spectral data are given for some selenoamides and selenourea.

On the electronic structure of disulfur dinitride, S2N2: comments on the applicability of semi-empirical energy band methods for polysulfur nitride, (SN)x

Abstract The conformational MO study of S 2 N 2 showed that a minimal basis set ab initio method gives much more reasonable results than the semi-empirical extended Huckel and the CNDO/2 method. The charge distribution is also most reasonable in the ab initio study. As a byproduct this implies some drawbacks of recent semi-empirical treatments of polysulfur nitride, (SN) x , too.

The numerical solution of the BGYB equation for the liquid-vapour interface

The derivation of the Born-Green-Yvon-Bogolyubov integrodifferential equation is discussed. As the numerical solution of this equation is very sensitive to the approximations it is pointed out that qualitative differences between the density profiles obtained with different approximations can be expected. The connection between the predictions of linear response theory and the behaviour of the resulting density profiles is also indicated.