Optimal generalized internal vibrational coordinates for symmetrical linear triatomic molecules

The use of generalized internal vibrational coordinates to describe vibrati onal motions in symmetrical linear triatomic molecules is considered. These coordinates are defined as the magnitudes of two generalized internal vect ors and the angle formed between them, and they depend on two parameters wh ich can be properly optimized. We derive an analytical expression which pro vides the optimal values of these parameters for linear symmetrical triatom ic molecules. The validity of this expression is checked by making variatio nal calculations of vibrational energy levels for the CO, and CS, molecules . (C) 1998 Elsevier Science B.V. All rights reserved.