ИСТИНА

Force field matrices of extended molecular systems with non-covalent interactions (clusters, polymers etc.) can be constructed on a base of regularized scaled quantum mechanical hessians of separate molecules which were fitted to experimentl data just in Cartesian coordinates. The next scheme for the calculations of vibrational spectra of the large size molecules such as polymers, nanostructures, biological systems, etc. can be proposed: 1) preliminary quantum mechanical analysis of moderate size molecules chosen as key or model molecules which are the fragments of large molecular systems; 2) the fitting ab initio Hessians of separate blocks to experimental data (vibrational spectra) in Cartesian coordinates within scaling procedure; 3) synthesis (construction) the Hessian of a large molecular system from separate regularizzed fragments and calculation of its vibrational spectra and thermodynamical functions. These calculations may be performed with our software packages SPECTRUM and CART