Two projector triple products in quantum crystallography
The results presented in this paper are patterned upon a presentation by L. M. entitled “Quantum Crystallography: N-representability Big and Small” during the Premier Quantum Crystallography Online Meeting (QCrOM2020) at Centrale Supélec, Paris, 26-29 August 2020.
Funding information: Canada Foundation for Innovation, Grant/Award Number: CFI-Leaders Opportunity Fund Grant 2019; Natural Sciences and Engineering Research Council of Canada, Grant/Award Number: NSERC-DG 2015; Mount Saint Vincent University; PSC CUNY Award, Grant/Award Number: 63842-00 41; U.S. Naval Research Laboratory, Grant/Award Number: 47203-00 01
Abstract
Consider a projector matrix P, representing the first order reduced density matrix in a basis of orthonormal atom-centric basis functions. A mathematical question arises, and that is, how to break P into its natural component kernel projector matrices, while preserving N-representability of
. The answer relies upon 2-projector triple products, P′jPP′j. The triple product solutions, applicable within the quantum crystallography of large molecules, are determined by a new form of the Clinton equations, which—in their original form—have long been used to ensure N-representability of density matrices consistent with X-ray diffraction scattering factors. As such, the goal of this paper is to outline a possible pathway for the application of quantum crystallography to crystals of large molecular systems.
Open Research
DATA AVAILABILITY STATEMENT
Data sharing not applicable - no new data generated, or the article describes entirely theoretical research