Analytic gradients for coupled-cluster energies that include noniterative connected triple excitations: Application to cis- and trans-HONO

Timothy J. Lee, Alistair P. Rendell

Research output: Contribution to journalArticlepeer-review

168 Citations (Scopus)

Abstract

An efficient formulation of the analytic energy gradient for the single and double excitation coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T), is presented. The formulation presented here has a smaller computational cost than any previous formulation, and the algebraic manipulations that lead to the additional savings may be applied generally to the analytic gradient of Møller-Plesset perturbation theory energies. The energy contribution from connected triple excitations scales as no 3n v 4 + no 4nv 3, and the additional work needed for the gradient scales as 2no 3nv 4 + 2no 4n v 3, where no is the number of doubly occupied orbitals and nv is the number of unoccupied orbitals. The new formulation has been implemented in an efficient set of programs that utilize highly vectorized algorithms and has been used to investigate the equilibrium structures, harmonic vibrational frequencies, infrared intensities, and energy separation of cis-and trans-HONO.

Original languageEnglish
Pages (from-to)6229-6236
Number of pages8
JournalThe Journal of Chemical Physics
Volume94
Issue number9
DOIs
Publication statusPublished - 1 May 1991
Externally publishedYes

Fingerprint Dive into the research topics of 'Analytic gradients for coupled-cluster energies that include noniterative connected triple excitations: Application to cis- and trans-HONO'. Together they form a unique fingerprint.

Cite this