Format

Send to

Choose Destination
See comment in PubMed Commons below
J Chem Phys. 2004 Feb 15;120(7):3059-65.

Vibrational zero-point energies and thermodynamic functions beyond the harmonic approximation.

Author information

  • 1Laboratorio di Struttura e Dinamica Molecolare, Dipartimento di Chimica, Universita "Federico II," Complesso Universitario Monte Sant' Angelo, Via Cintia, I-80126 Napoli, Italy. baronev@unina.it

Abstract

This paper compares harmonic and anharmonic zero-point energies and thermodynamic functions for a number of molecules of small and medium size. Anharmonic corrections cannot be neglected for quantitative studies, but can be obtained quite effectively by a perturbative treatment including cubic force constants to the second order and semidiagonal quartic constants to the first order. Simple finite difference equations provide all the necessary terms by at most 6N-11 Hessian evaluations, where N is the number of atoms in the system. Accurate values are obtained by this method using the Becke three parameter Lee-Yang-Parr functional, medium size basis sets, and, when needed, proper treatment of internal rotations. The whole model has been completely automated in the Gaussian package.

PMID:
15268458
DOI:
10.1063/1.1637580
[PubMed]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for American Institute of Physics
    Loading ...
    Support Center