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RESEARCH PRODUCT

Interacting induced dipoles polarization model for molecular polarizabilities. Reference molecules, amino acids and model peptides

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Abstract We outline a method for the calculation of molecular dipole ( μ ) and quadrupole ( Θ = ) moments and dipole–dipole polarizabilities ( α = ) which we have successfully applied to a series of reference molecules, amino acids and model peptides. The results for μ are in line with CPHF reference calculations. In particular, the calculated positive value of CO is in agreement with both experimental and CI calculations. The computation of ( α = ) has been performed by the interacting induced dipoles polarization model that calculates tensor effective anisotropic point polarizabilities (method of Applequist et al.). The POLAR program cannot be used as a black box. Some tests should be performed when a new molecule is calculated. The POLAR program was designed for large molecules. Although in some large molecules the POLAR program has been successfully applied to predict trends, the test with small molecules shows that we have to touch up the approximations along the formulation. The results for ( α = ) of reference molecules are shown better for the POLAR program than for the PAPID algorithm. In the former case, the POLAR-AP model is revealed superior to the POLAR-IP method. The results for the amino acids and model peptides show that, as a rule, the PAPID program produces the better results, while the POLAR program produces acceptable results and converges in all the cases. In general, POLAR-IP underestimates the molecular polarizabilities and anisotropies while POLAR-AP overestimates these properties.