2013-Constraints on the values of force constants based on quantum mechanical calculations.Generalized inverse structural problem. Computer implementation.-Examples of molecular force field calculations within different models.

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The molecular dynamic algorithm for simulation of thin-film growth is reported. The achieved performance of this algorithm is sufficient for detailed investigations of structural effects in thin films with practically meaningful dimensions.

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The IR spectra of gaseous nitrobenzene (NB) and its 15 N isotopomer have been obtained in the frequency range of 3500-250 cm -1 , and the far-IR spectra of their solutions and the NB neat liquid sample have been recorded in the range of 600-30 cm -1 . A detailed description of the spectra of NB and 1,3,5-trinitrobenzene (sym-TNB) and their isotopomers has been accomplished using the force fields calculated at the MP2(full)/aug-cc-pVTZ and MP2(full)/cc-pVTZ levels. Transferability of the refined scale factors for the calculated force constants obtained by the Pulay technique has been used to provide evidence for validity of both interpreting the NB and sym-TNB spectra and refining the calculated force fields. The direct and inverse spectral problems have been solved by variational technique to determine torsional energy levels and refine the potential function by optimizing the V k coefficients in its Fourier series expansion. The height of the MP2(full) barrier to internal rotation has been reduced from 5.5 to 4.5 kcal/mol due to extension of the used basis set from 6-31(d,p) to aug-cc-pVTZ. The method of joint dynamic structural analysis of the GED, MW, and vibrational spectroscopy, and ab initio data in terms of the PES parameters have been applied to investigation of equilibrium geometry and internal rotation in the nonrigid NB and sym-TNB molecules having one and three coupled internal rotors, respectively. The experimental r e -parameter values of both molecules (C 2v and D 3h point group symmetries) are in agreement with those obtained by ab initio calculations. This paper is dedicated to Professor Magdolna Hargittai on the occasion of her 70th birthday.

In this paper we present a computationally effective approach to classical molecular dynamic simulation of thin film growth with orientation on cluster supercomputing facilities. The goal of the developed approach is to investigate structural heterogeneities of thin films deposited on substrates at a nanoscale level. These heterogeneities depend on the experimental conditions of a deposition process being used. They have essential influence on practical properties of thin films and their modeling is important for achieving further progress in thin film optical technology.The presented research is focused on silicon dioxide thin films growth. A special force field, oriented on the atomistic description of the silicon dioxide deposition on fused silica substrate, has been developed and applied to the molecular dynamic simulation with the GROMACS package. The validity of the developed simulation approach is verified using atomic clusters consisting of up to 10 6 atoms and having characteristic dimensions of up to 30 nm. Its computational efficiency is tested using up to 2048 cores. The dependence of achievable efficiency on model parameters is discussed.