Abstract
Analytical formulas are reported for the nonlinear transformation of cubic and quartic force constants from normal coordinates to cartesian coordinates. At the equilibrium reference geometry the first and higher partial derivatives with respect to space-fixed cartesian coordinates are evaluated for the body-fixed normal coordinates, for the rotation matrix elements relating the space-fixed frame and the body-fixed Eckart frame, and for other matrix elements. The computational implementation of the transformation is outlined. The proposed formalism is valid for nonlinear molecules.
