Biomedical subjects

O V Prezhdo

Publications and source records attributed to O V Prezhdo.

3 recordsLinked to original sources

PubMed2006

Hole-particle characterization of coupled-cluster singles and doubles and related models.

The hole-particle analysis introduced in the paper [J. Chem. Phys. 124, 224109 (2006)] is fully described and extended for coupled-cluster models of practical importance. Based on operator renormalization of the conventional amplitudes t(ai) and t(ab,ij), we present a simplified method for estimating the hole-particle density matrices for coupled-cluster singles and doubles (CCSD). With this procedure we convert the first-order density matrix of the configuration interaction (CI) singles and doubles (CISD) model, which lacks size consistency, into an approximately size-consistent expression. This permits us to correctly estimate specific indices for CCSD, including the hole and particle occupation numbers for each atom, the total occupation of holes/particles, and the entropylike measure for effective unpaired geminals. Our calculations for simple diatomic and triatomic systems indicate reasonable agreement with the full CI values. For CCSD and CISD we derive special types of two-center indices, which are similar to the charge transfer analysis of excited states previously given within the CIS model. These new quantities, termed charge transfer correlation indices, reveal the concealed effects of atomic influence on electronic redistribution due to electron correlation.

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PubMed2006

Analysis of multiconfigurational wave functions in terms of hole-particle distributions.

A detailed study of hole-particle distributions in many-electron molecular systems is presented, based on a representation of the high-order density matrices obtained by an operator technique reminiscent of Bogolyubov's quantum statistical operator theory. A rigorous definition of density matrices of arbitrary order is given for a composite system of holes and particles. Particular attention is focused on the description of mixed hole-particle distributions. The main results are given as the functionals of excitation operators (generators) that are used in the conventional configuration interaction (CI) and coupled cluster (CC) theories. Local atomic occupation numbers for holes and particles are introduced to provide a measure of the participation of specific atoms in the electron correlation processes. The corresponding total occupations--as well as the hole-hole, particle-particle, and hole-particle mean distances--provide a useful and physically intuitive description of electron correlation. Suitable computational schemes for numerical evaluation of the above characteristics within full CI and typical CC approaches are presented. The insights one can gain with the developed approach into the peculiarities and nuances of the hole-particle picture in typical electronic processes such as excitation and molecular dissociation are illustrated with specific computations on small molecules and closed-shell atoms.

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PubMed2001

Quantum backreaction through the Bohmian particle.

A novel solution to the quantum backreaction problem in a mixed quantum-classical simulation is provided using the Bohmian interpretation of quantum mechanics. The Bohmian backreaction is unique, computationally simple, features reaction channel branching, and easily gives the full classical limit. The Bohmian quantum-classical method is illustrated by application to a model of O2 interacting with a Pt surface.

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