When is an internal rotation a vibration?
Abstract
Calculation of entropies for molecules having internal rotations are in error if these rotations are treated as vibrations. Using MNDO-calculated geometries, entropies of a set of molecules were calculated assuming all internal motions were vibrations. Errors were determined for these molecules, with particular attention paid to the ones containing internal rotations. Based on the total internal partition functions calculated in this manner compared to total internal partition functions calculated by assuming a free rotor for the internal rotation we developed a criterion for determining when the free rotor correction needs to be made to the entropy values. The correction greatly improves the calculated entropy for molecules with internal rotation.
- Publication:
-
Interim Report
- Pub Date:
- August 1983
- Bibcode:
- 1983afa..rept.....L
- Keywords:
-
- Entropy;
- Molecular Orbitals;
- Rotation;
- Vibration;
- Comparison;
- Computer Programs;
- Correction;
- Errors;
- Physical Chemistry;
- Prediction Analysis Techniques;
- Atomic and Molecular Physics