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Title: Semiclassical Monte Carlo: A first principles approach to non-adiabatic molecular dynamics

Modeling the dynamics of photophysical and (photo)chemical reactions in extended molecular systems is a new frontier for quantum chemistry. Many dynamical phenomena, such as intersystem crossing, non-radiative relaxation, and charge and energy transfer, require a non-adiabatic description which incorporate transitions between electronic states. Additionally, these dynamics are often highly sensitive to quantum coherences and interference effects. Several methods exist to simulate non-adiabatic dynamics; however, they are typically either too expensive to be applied to large molecular systems (10's-100's of atoms), or they are based on ad hoc schemes which may include severe approximations due to inconsistencies in classical and quantum mechanics. We present, in detail, an algorithm based on Monte Carlo sampling of the semiclassical time-dependent wavefunction that involves running simple surface hopping dynamics, followed by a post-processing step which adds little cost. The method requires only a few quantities from quantum chemistry calculations, can systematically be improved, and provides excellent agreement with exact quantum mechanical results. Here we show excellent agreement with exact solutions for scattering results of standard test problems. Additionally, we find that convergence of the wavefunction is controlled by complex valued phase factors, the size of the non-adiabatic coupling region, and the choice of sampling function.more » These results help in determining the range of applicability of the method, and provide a starting point for further improvement.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [4] ;  [1] ;  [2] ;  [5] ;  [1]
  1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. (CNLS), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  3. (Ukraine)
  4. (United States)
  5. (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Publication Date:
OSTI Identifier:
22415335
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 18; 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; CHEMICAL REACTIONS; COUPLING; ENERGY TRANSFER; EXACT SOLUTIONS; MOLECULAR DYNAMICS METHOD; MONTE CARLO METHOD; QUANTUM MECHANICS; RELAXATION; SCATTERING; SEMICLASSICAL APPROXIMATION; SIMULATION; TIME DEPENDENCE; WAVE FUNCTIONS