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Mean Field Approximation (mean + field_approximation)

Distribution by Scientific Domains

Physics and Astronomy	50%
Chemistry	50%

Selected Abstracts

Parallelization of the quantum dynamics code for cluster architecture and its applications to the Gross,Pitaevskii equation

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2006
Adam Gorecki
Abstract We present a parallel version of a quantum dynamics (QD) algorithm in a wave function representation. The algorithm has been optimized for a Linux cluster as well as for Cray T3E, using a parallel version of a three-dimensional FFT library. We have applied this algorithm for solving the nonlinear Gross,Pitaevskii equation (GPE), which describes the evolution of Bose,Einstein condensates (BEC) in the mean field approximation. Our method reduces the computational time and allows the study of nonlinear quantum systems. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]

A new method to locate saddle points for reactions in solution by using the free-energy gradient method and the mean field approximation

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2004
I. Fdez.
Abstract A new method for calculating saddle points of reactions in solution is presented. The main characteristics of the method are: (1) the solute,solvent system is described by the averaged solvent electrostatic potential/molecular dynamics method (ASEP/MD). This is a quantum mechanics/molecular mechanics method (QM/MM) that makes use of the mean field approximation (MFA) and that permits one to simultaneously optimize the electronic structure and geometry of the solute molecule and the solvent structure around it. (2) The transition state is located by the joint use of the free-energy gradient method and the mean field approximation. An application to the study of the Menshutkin reaction between NH3 and CH3Cl in aqueous solution is discussed. The accuracy and usefulness of the proposed method is checked through comparison with other methods. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1227,1233, 2004 [source]

Magnetic impurity transition in a (d,+,s)-wave superconductor

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2010
L. S. BorkowskiArticle first published online: 8 FEB 2010
Abstract We consider the superconducting state of symmetry with finite concentration of Anderson impurities in the limit . The model consists of a BCS-like term in the Hamiltonian and the Anderson impurity treated in the self-consistent large- N mean field approximation. Increasing impurity concentration or lowering the ratio drives the system through a transition from a state with two sharp peaks at low energies and exponentially small density of states at the Fermi level to one with . This transition is discontinuous if the energy of the impurity resonance is the smallest energy scale in the problem. [source]

Theory of the cubic-tetragonal phase transition in PbTiO3

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006
Es-saïd El-frikhe
Abstract The phase transition in PbTiO3 is discussed quantitatively from the microscopic free energy based upon the mean field approximation, where the Ti ions shift is considered as the order parameter in the lattice having the spontaneous deformation. From our calculation of the microscopic free energy, the ionic shift of the Ti ion and the coefficient of the expanded free energy, we concluded that the transition temperature and the order of cubic-tetragonal transition are well explained by this model. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Baryons as Fock states of 3,5, ... quarks ,

ANNALEN DER PHYSIK, Issue 11-12 2004
D. Diakonov
Abstract We present a generating functional producing quark wave functions of all Fock states in the octet, decuplet and antidecuplet baryons in the mean field approximation, both in the rest and infinite momentum frames. In particular, for the usual octet and decuplet baryons we get the SU(6)-symmetric wave functions for their 3-quark component but with specific corrections from relativism and from additional quark-antiquark pairs. For the exotic antidecuplet baryons we obtain the 5-quark wave function. [source]