Mass derivatives of molecular parameters and distortions in r(m)((2)) structures

Expressions are derived for the derivatives of various molecular vibration- rotation parameters with respect to atomic masses. These are applied to det ermine an expression for the mass derivatives of the zero-point moments of inertia, and hence the theoretical substitution coordinates. It is then pos sible to calculate the distortions in structures determined by means of the , r(m)((2)) method. The latter agree well with the distortions found in r(m )((2)) fits of synthetic data. (C) 2001 Academic Press.