Time-Independent Coupled-Cluster Theory of the Polarization Propagator

• Published in: Collection of Czechoslovak chemical communications Vol. 70; no. 8; pp. 1109 - 1132
• Main Authors: Moszynski, Robert, Żuchowski, Piotr S., Jeziorski, Bogumił
• Format: Journal Article
• Language: English
• Published: Prague Blackwell Publishing Ltd 01.08.2005
• Subjects: Chemistry
• ISSN: 0010-0765; 1212-6950; 2192-6506
• DOI: 10.1135/cccc20051109

A novel, time-independent formulation of the coupled-cluster theory of the polarization propagator is presented. This formulation, unlike the equation-of-motion coupled-cluster approach, is fully size-extensive and, unlike the conventional time-dependent coupled-cluster method, is manifestly Hermitian, which guarantees that the polarization propagator is always real for purely imaginary frequencies and that the resulting polarizabilities exhibit time-reversal symmetry (are even functions of frequency) for purely real or purely imaginary perturbations. This new formulation is used to derive compact expressions for the three leading terms in the Møller-Plesset expansion for the polarization propagator. The true and apparent correlation contributions to the second-order term are analyzed and separated at the operator level. Explicit equations for the polarization propagator at the non-perturbative, singles and doubles level (CCSD) are presented.