Seminar: Fred Manby

Centre for Computational Chemistry, School of Chemistry,  University of Bristol

 Antisymmetry and Molecular Dissociation in Coupled-Cluster Theory

Wednesday December 11, 2013, 2:00 PM
150 Chevron Science Center

 

Coupled-cluster theory offers an accurate and systematically improvable description of molecular electronic structure. One approximation in the scheme, CCSD(T), is referred to as ‘the gold standard’ of quantum chemistry. It is therefore a bit disturbing that it fails to describe that most chemical process, the dissociation of a covalent bond. Here the failure of approximate coupled-cluster theories in this situation will be presented from the viewpoint of fermionic antisymmetry, and a modified version of coupled cluster theory will be discussed. The doubles theory in the new framework has all of the pleasing properties of CCSD, but dissociates molecules to a zero-force asymptote, and performs about as well as CCSD(T) for energetics close to equilibrium structures.