THE CALCULATIONS OF SMALL MOLECULAR-CONFORMATION ENERGY DIFFERENCES BY DENSITY FUNCTIONAL METHOD

The differences in the conformational energies for the gauche (G) and trans (T) conformers of 1,2-difluoroethane and for myo- and scyllo-conformer of inositol have been calculated by local density functional method (LDF approximation) with geometry optimization using different sets of calculation parameters. It is shown that in contrast to Hartree-Fock methods, density functional calculations reproduce the correct sip and value of the gauche effect for 1,2-difluoroethane and energy difference for both conformers of inositol. The results of normal vibrational analysis for 1,2-difluoroethane showed that harmonic frequencies calculated in LDF approximation agree with experimental data with the accuracy typical for scaled large basis set Hartree-Fock calculations.