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Title: Variational mixed quantum/semiclassical simulation of dihalogen guest and rare-gas solid host dynamics

A variational mixed quantum-semiclassical theory for the internal nuclear dynamics of a small molecule and the induced small-amplitude coherent motion of a low-temperature host medium is developed, tested, and used to simulate the temporal evolution of nonstationary states of the internal molecular and surrounding medium degrees of freedom. In this theory, termed the Fixed Vibrational Basis/Gaussian Bath (FVB/GB) method, the system is treated fully quantum mechanically while Gaussian wave packets are used for the bath degrees of freedom. An approximate time-dependent wave function of the entire model is obtained instead of just a reduced system density matrix, so the theory enables the analysis of the entangled system and bath dynamics that ensues following initial displacement of the internal-molecular (system) coordinate from its equilibrium position. The norm- and energy-conserving properties of the propagation of our trial wave function are natural consequences of the Dirac-Frenkel-McLachlan variational principle. The variational approach also stabilizes the time evolution in comparison to the same ansatz propagated under a previously employed locally quadratic approximation to the bath potential and system-bath interaction terms in the bath-parameter equations of motion. Dynamics calculations are carried out for molecular iodine in a 2D krypton lattice that reveal both the time-course ofmore » vibrational decoherence and the details of host-atom motion accompanying energy dissipation and dephasing. This work sets the stage for the comprehensive simulation of ultrafast time-resolved optical experiments on small molecules in low-temperature solids.« less
Authors:
 [1] ;  [2]
  1. Department of Physics, and Oregon Center for Optics, University of Oregon, Eugene, Oregon 97403 (United States)
  2. Department of Chemistry and Biochemistry, and Oregon Center for Optics, University of Oregon, Eugene, Oregon 97403 (United States)
Publication Date:
OSTI Identifier:
22419883
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 97 MATHEMATICAL METHODS AND COMPUTING; ATOMS; DEGREES OF FREEDOM; DENSITY MATRIX; EQUATIONS OF MOTION; INTERACTIONS; IODINE; KRYPTON; MOLECULES; SEMICLASSICAL APPROXIMATION; SIMULATION; SOLIDS; TIME DEPENDENCE; TIME RESOLUTION; WAVE FUNCTIONS; WAVE PACKETS