A MP2 four-dimensional potential energy surface of dimethyl-amine

摘要

In this article, the four-dimensional potential energy surface for the double methyl torsion, CNC angle and amine hydrogen wagging in dimethyl-amine was determined using fully optimized MP2/6-31G(d, p) calculations. These four coordinates correspond to the largest amplitude vibrations and confer the non-rigidity properties of the molecule. Calculations of 825 nuclear conformations selected by symmetry considerations and energy criteria, were performed. They have been fitted to an equation which is a sum of a gaussian function and a product of a double Fourier series multiplied by a double Taylor series. The total number of the coefficients are 87. They are the exponent of the gaussian function and 86 linear coefficients. The most significant parameters of this potential are also analyzed. They are the inversion barrier, the torsional barrier and the gearing interaction term between the methyl groups and they are defined as hypersurfaces depending on two or three coordinates. The shape of these surfaces has an important effect on the frequencies.