The Experts below are selected from a list of 4065 Experts worldwide ranked by ideXlab platform
Shiwei Zhang - One of the best experts on this subject based on the ideXlab platform.
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communication calculation of interatomic forces and optimization of molecular geometry with auxiliary field quantum monte carlo
Journal of Chemical Physics, 2018Co-Authors: Mario Motta, Shiwei ZhangAbstract:We propose an algorithm for accurate, systematic, and scalable computation of interatomic forces within the auxiliary-field quantum Monte Carlo (AFQMC) method. The algorithm relies on the Hellmann-Feynman Theorem and incorporates Pulay corrections in the presence of atomic orbital basis sets. We benchmark the method for small molecules by comparing the computed forces with the derivatives of the AFQMC potential energy surface and by direct comparison with other quantum chemistry methods. We then perform geometry optimizations using the steepest descent algorithm in larger molecules. With realistic basis sets, we obtain equilibrium geometries in agreement, within statistical error bars, with experimental values. The increase in computational cost for computing forces in this approach is only a small prefactor over that of calculating the total energy. This paves the way for a general and efficient approach for geometry optimization and molecular dynamics within AFQMC.
Francisco M Fernandez - One of the best experts on this subject based on the ideXlab platform.
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on the hellmann feynman Theorem for degenerate states
arXiv: Quantum Physics, 2019Co-Authors: Francisco M FernandezAbstract:In this paper we discuss the validity of the Hellmann-Feynman Theorem (HFT) for degenerate states. We derive it in a general way and apply it to simple illustrative examples. We also analyze a recent paper that shows results that apparently suggest that the HFT does not apply to degenerate states.
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the hellmann feynman Theorem for statistical averages
Journal of Mathematical Chemistry, 2014Co-Authors: Francisco M FernandezAbstract:We discuss the Hellmann–Feynman Theorem for degenerate states and its application to the calculation of the derivatives of statistical averages with respect to external parameters.
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comment on breakdown of the hellmann feynman Theorem degeneracy is the key
Physical Review B, 2004Co-Authors: Francisco M FernandezAbstract:We show that the Hellmann-Feynman Theorem is valid for degenerate states provided that they are chosen to satisfy a simple criterion that removes a recently discussed ambiguity.
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the extended hellmann feynman Theorem revisited
Chemical Physics Letters, 1995Co-Authors: Francisco M FernandezAbstract:Abstract We give a simpler, shorter and more general proof of the extended Hellmann-Feynman Theorem commonly applied to the calculation of forces between classical and quantal particles.
Mario Motta - One of the best experts on this subject based on the ideXlab platform.
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communication calculation of interatomic forces and optimization of molecular geometry with auxiliary field quantum monte carlo
Journal of Chemical Physics, 2018Co-Authors: Mario Motta, Shiwei ZhangAbstract:We propose an algorithm for accurate, systematic, and scalable computation of interatomic forces within the auxiliary-field quantum Monte Carlo (AFQMC) method. The algorithm relies on the Hellmann-Feynman Theorem and incorporates Pulay corrections in the presence of atomic orbital basis sets. We benchmark the method for small molecules by comparing the computed forces with the derivatives of the AFQMC potential energy surface and by direct comparison with other quantum chemistry methods. We then perform geometry optimizations using the steepest descent algorithm in larger molecules. With realistic basis sets, we obtain equilibrium geometries in agreement, within statistical error bars, with experimental values. The increase in computational cost for computing forces in this approach is only a small prefactor over that of calculating the total energy. This paves the way for a general and efficient approach for geometry optimization and molecular dynamics within AFQMC.
Sokrates T Pantelides - One of the best experts on this subject based on the ideXlab platform.
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hellmann feynman Theorem and the definition of forces in quantum time dependent and transport problems
Physical Review B, 2000Co-Authors: Massimiliano Di Ventra, Sokrates T PantelidesAbstract:The conventional Hellmann-Feynman Theorem for the definition of forces on nuclei is not directly applicable to quantum time-dependent and transport problems. We present a rigorous derivation of a general Hellmann-Feynman-like Theorem that applies to all quantum mechanical systems and reduces to well-known results for ground-state problems. It provides a rigorous definition of forces in time-dependent and transport problems. Explicit forms of Pulay-like forces are derived and the conditions for them to be zero are identified. A practical scheme for ab initio calculations of current-induced forces is described and the study of the transfer of a Si atom between two electrodes is presented as an example.
Piotr Bala - One of the best experts on this subject based on the ideXlab platform.
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extended hellmann feynman Theorem for non stationary states and its application in quantum classical molecular dynamics simulations
Chemical Physics Letters, 1994Co-Authors: Piotr Bala, Bogdan Lesyng, J A MccammonAbstract:Abstract An extended Hellmann-Feynman Theorem for non-stationary states is presented. For systems in which some particles are described quantum-mechanically and others classically, the extended Theorem allows one to determine more precisely the forces exerted by quantum particles on classical particles. The forces are used in quantum-classical molecular dynamics (QCMD) simulations, where the extended Theorem allows an increase in the integration time-step and a reduction in the energy drift. The QCMD model also accounts for a dynamical vibronic coupling between quantum and classical subsystems, which further improves the quality of the simulation results.