2016/08/18 by Luning Zhao, Zhao, Luning, Eric Neuscamman +1 · 1 citation
Physics and Astronomy · Chemical Engineering · #Spectroscopy and Quantum Chemical Studies #Catalysis and Oxidation Reactions #Advanced Chemical Physics Studies
paper · pdf · doi:10.48550/arxiv.1608.05195
Recently developed pair coupled cluster doubles (pCCD) theory successfully reproduces doubly occupied configuration interaction (DOCI) with mean field cost. However, the projective nature of pCCD makes the method non-variational and thus hard to improve systematically. As a variational alternative, we explore the idea of coupled-cluster-like expansions based on amplitude determinants and develop a specific theory similar to pCCD based on determinants of pairwise doubles. The new ansatz admits a variational treatment through Monte Carlo methods while remaining size-consistent and, crucially, polynomial cost. In the dissociations of LiH, HF, H2O and N2, the method performs very similarly to pCCD and DOCI, suggesting that coupled-cluster-like ansatzes and variational evaluation may not be mutually exclusive.