Analytical approach for the tunneling process in double well potentials using IRC calculations

A novel strategy to applying the analytical solution of the Schrodinger equation via angular prolate spheroidal (APS) function was developed. It provides a simple and accurate approach to calculating the energy levels, splitting and tunneling frequency in symmetrical double well potentials. The strategy consists of modeling the potential energy surface (PES) with an appropriate intrinsic reaction coordinate (IRC) curve, and its fitting to the solvable symmetric trigonometric potential. The parameter L is solved via the variation method. The accuracy was tested against using the same steps with the WKB method and the instanton-soliton approach to NH3, ND3 and methyl substituted amines. For NH3, the tunneling frequencies were 2.56, 3.67 and 1.12 x 10(10) s(-1), using the APS function, WKB and instanton approaches respectively, while the experimental is 2.38 x 10(10) s(-1). The results show that it produced the most accurate results with a straightforward calculation, and in regions where the semi-classical fails.