✦ LIBER ✦

Converging the single-reference coupled-cluster equations

✍ Scribed by Nevin Oliphant; Ludwik Adamowicz

Publisher: Elsevier Science
Year: 1992
Tongue: English
Weight: 479 KB
Volume: 190
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(92)86094-x

No coin nor oath required. For personal study only.

✦ Synopsis

A scheme for stabilizing the reduced linear equation method of solving the single-reference coupled system of equations is developed and implemented. When one or more secondary determinants become as important as the primary determinant in describing the chemical system, numerical instabilities frequently arise in the procedure of solving the coupled-cluster equations. This is avoided by "quasi-linearizing" certain non-linear terms in the equations and including them with the linear terms. A study on the LiH molecule with an internuclear separation of 9.045 au is used to demonstrate the effectiveness of this procedure.

📜 SIMILAR VOLUMES

Multiple solutions of the single-referen

Multiple solutions of the single-reference coupled-cluster method

✍ Leszek Meissner; Anna Balková; Rodney J. Bartlett 📂 Article 📅 1993 🏛 Elsevier Science 🌐 English ⚖ 696 KB

The nonlinear coupled-cluster (CC) equations possess several solutions. They describe various excited states as long as they contain a contribution from the reference function. We study the additional solutions of the single-reference CC equations and demonstrate that unlike the ground state, the ap

Complete active space coupled-cluster me

Complete active space coupled-cluster method. Extension of single-reference coupled-cluster method using the CASSCF wavefunction

✍ Leszek Z. Stolarczyk 📂 Article 📅 1994 🏛 Elsevier Science 🌐 English ⚖ 471 KB

It is proposed that the calculation of non-dynamical electronic correlation effects by the complete active space self-consistent field (CASSCF) method can be extended by the inclusion of dynamical correlation effects through the use of a suitably modified single-reference coupled-cluster (CC) proced

Convergence of the coupled-cluster singl

Convergence of the coupled-cluster singles, doubles and triples method

✍ Gary W. Trucks; Jozef Noga; Rodney J. Bartlett 📂 Article 📅 1988 🏛 Elsevier Science 🌐 English ⚖ 541 KB

The convergence of coupled-cluster equations for several cases, CCD, CCSD, CCSDT-n and the full CCSDT is investigated. Comparisons are made between the reduced linear equation (RLE) method for accelerating convergence and simple geometric extrapolation techniques, and between energy and wavefunction

Convergence of the coupled-cluster singl

Convergence of the coupled-cluster singles, doubles and triples method

✍ G.W. Trucks; J. Noga; R.J. Bartlett 📂 Article 📅 1988 🏛 Elsevier Science 🌐 English ⚖ 57 KB

With the help of G. Scuseria and H.F. Schaefer III, we have found an improper factor of 2 in non-linear HN T: contributions to T, amplitudes only for the fill CCSDT results

Applicability of single-reference couple

Applicability of single-reference coupled-cluster methods to excited states. A model study

✍ J. Jankowski; K. Kowalski; P. Jankowski 📂 Article 📅 1994 🏛 Elsevier Science 🌐 English ⚖ 637 KB

It is demonstrated that standard single-reference coupled-cluster @R-CC) theories can be successfully applied to the studies of some excited states not belonging to the lowest energy in their symmetry class. The prerequisite of such applications is that a proper reference state configuration and orb

The equation-of-motion coupled-cluster m

The equation-of-motion coupled-cluster method. Applications to open- and closed-shell reference states

✍ Donald C. Comeau; Rodney J. Bartlett 📂 Article 📅 1993 🏛 Elsevier Science 🌐 English ⚖ 803 KB

The equationof-motion coupled-cluster method (EOM-CCSD) and its quadratic CI (EOM-QCISD) variant for excited states have been implemented in the ACES II program system. Results for open-and closed-shell reference states are reported for Be, N2, CO, 02, and 0,. The results show that EOM-CCSD and EOM-