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Expressing molecular electron densities as linear combinations of Guassian 15 spherical functions extends accurate computations of ab initio quantum molecular similarity measures to large systems. These approximate least squares fitted functions lose the density of probability statistical meaning since some coefficients might be negative. A new algorithm using positive coefficients only and thus providing an electron density picture as a superposition of atomic shells is presented.

Articles you may be interested inPerturbative triples corrections in state-specific multireference coupled cluster theory J. Chem. Phys. 132, 074107 (2010); 10.1063/1.3305335Atomic orbital Laplace-transformed second-order Møller-Plesset theory for periodic systems Linear scaling coupled cluster and perturbation theories in the atomic orbital basis Property calculations using perturbed orbitals via state-specific multireference coupled-cluster and perturbation theories A reformulation of the perturbative triples correction to coupled cluster singles and doubles ͑CCSD͒ based on the numerical Laplace transform of the energy denominator is presented. Rearranged equations reduce the O(N 7 ) canonical scaling to O(N 6 ), where N is a size measure of the electronic system. Two to three quadrature points is adequate for chemical predictions. The Laplace ansatz permits simple, noniterative expressions in noncanonical orbital representations. Furthermore, substituting canonical by generalized CCSD natural orbitals, the Laplace ansatz exhibits scaling close to O(N 5 ), while retaining accuracy and providing crossover with respect to canonical triples for small size systems. A developing atomic orbital formulation is also introduced.

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