A local coherent-state approximation to system-bath quantum dynamics
- Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20133 Milan (Italy) and CIMAINA, University of Milan, Via Golgi 19, 20133 Milan (Italy)
A novel quantum method to deal with typical system-bath dynamical problems is introduced. Subsystem discrete variable representation and bath coherent-state sets are used to write down a multiconfigurational expansion of the wave function of the whole system. With the help of the Dirac-Frenkel variational principle, simple equations of motion--a kind of Schroedinger-Langevin equation for the subsystem coupled to (pseudo) classical equations for the bath--are derived. True dissipative dynamics at all times is obtained by coupling the bath to a secondary, classical Ohmic bath, which is modeled by adding a friction coefficient in the derived pseudoclassical bath equations. The resulting equations are then solved for a number of model problems, ranging from tunneling to vibrational relaxation dynamics. Comparison of the results with those of exact, multiconfiguration time-dependent Hartree calculations in systems with up to 80 bath oscillators shows that the proposed method can be very accurate and might be of help in studying realistic problems with very large baths. To this end, its linear scaling behavior with respect to the number of bath degrees of freedom is shown in practice with model calculations using tens of thousands of bath oscillators.
- OSTI ID:
- 20864340
- Journal Information:
- Journal of Chemical Physics, Vol. 125, Issue 19; Other Information: DOI: 10.1063/1.2362821; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
ANNIHILATION OPERATORS
APPROXIMATIONS
COMPARATIVE EVALUATIONS
COUPLING
DEGREES OF FREEDOM
EIGENSTATES
ENERGY TRANSFER
EQUATIONS OF MOTION
LANGEVIN EQUATION
OSCILLATORS
REACTION KINETICS
SCHROEDINGER EQUATION
TIME DEPENDENCE
TUNNEL EFFECT
VARIATIONAL METHODS
WAVE FUNCTIONS