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The State-Universal Multi-Reference Coupled-Cluster Theory: An Overview of Some Recent Advances
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Higher Energy Derivatives in Hilbert Space Multi-Reference Coupled Cluster Theory : A Constrained Variational Approach

Physical Chemistry Division, National Chemical Laboratory, Pune, India
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Int. J. Mol. Sci. 2002, 3(6), 710-732; https://0-doi-org.brum.beds.ac.uk/10.3390/i3060710
Received: 18 December 2001 / Accepted: 10 April 2002 / Published: 30 June 2002
(This article belongs to the Special Issue Multireference Quantum Chemical Methods)
In this paper, we present formulation based on constrained variational approach to compute higher energy derivatives upto third order in Hilbert Space Multi-Reference Coupled Cluster (HSMRCC) Theory. This is done through the use of a functional with Lagrange multipliers corresponding to HSMRCC method, as done by Helgaker, Jorgensen and Szalay. We derive explicit expressions upto third order energy derivatives. Using (2n + 1) and (2n + 2) rules, the cancellation of higher order derivatives of functional parameters that are not necessary according to these rules, is explicitly demonstated. Simplified expressions are presented. We discuss several aspects of the functional used and its potential implications. View Full-Text
Keywords: Energy Derivatives; Lagrange Multipliers; Constrained Variation; Hilbert Space Multi-Reference; Coupled Cluster Energy Derivatives; Lagrange Multipliers; Constrained Variation; Hilbert Space Multi-Reference; Coupled Cluster
MDPI and ACS Style

Shamasundar, K.R.; Pal, S. Higher Energy Derivatives in Hilbert Space Multi-Reference Coupled Cluster Theory : A Constrained Variational Approach. Int. J. Mol. Sci. 2002, 3, 710-732. https://0-doi-org.brum.beds.ac.uk/10.3390/i3060710

AMA Style

Shamasundar KR, Pal S. Higher Energy Derivatives in Hilbert Space Multi-Reference Coupled Cluster Theory : A Constrained Variational Approach. International Journal of Molecular Sciences. 2002; 3(6):710-732. https://0-doi-org.brum.beds.ac.uk/10.3390/i3060710

Chicago/Turabian Style

Shamasundar, K. R., and Sourav Pal. 2002. "Higher Energy Derivatives in Hilbert Space Multi-Reference Coupled Cluster Theory : A Constrained Variational Approach" International Journal of Molecular Sciences 3, no. 6: 710-732. https://0-doi-org.brum.beds.ac.uk/10.3390/i3060710

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