Nonadiabatic excited-state molecular dynamics: Numerical tests of convergence and parameters

• Autores: Nelson, Tammie; Fernández Alberti, Sebastián; Chernyak, Vladimir; Roitberg, Adrián; Tretiak, Sergei
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: nonadiabatic molecular dynamics; excited states
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Nonadiabatic molecular dynamics simulations, involving multiple Born-Oppenheimer potential energy surfaces, often require a large number of independent trajectories in order to achieve the desired convergence of the results, and simulation relies on different parameters that should be tested and compared. In addition to influencing the speed of the simulation, the chosen parameters combined with the frequently reduced number of trajectories can sometimes lead to unanticipated changes in the accuracy of the simulated dynamics. We have previously developed a nonadiabatic excited state molecular dynamics methodology employing Tullys fewest switches surface hopping algorithm. In this study, we seek to investigate the impact of the number of trajectories and the various parameters on the simulation of the photoinduced dynamics of distyrylbenzene (a small oligomer of polyphenylene vinylene) within our developed framework. Various user-defined parameters are analyzed: classical and quantum integration time steps, the value of the friction coefficient for Langevin dynamics, and the initial seed used for stochastic thermostat and hopping algorithms. Common approximations such as reduced number of nonadiabatic coupling terms and the classical path approximation are also investigated. Our analysis shows that, at least for the considered molecular system, a minimum of ∼400 independent trajectories should be calculated in order to achieve statistical averaging necessary for convergence of the calculated relaxation timescales.
Fil: Nelson, Tammie. Los Alamos National Laboratory; Estados Unidos
Fil: Fernández Alberti, Sebastián. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Chernyak, Vladimir. Wayne State University (wayne State University); Estados Unidos
Fil: Roitberg, Adrián. University of Florida; Estados Unidos
Fil: Tretiak, Sergei. Los Alamos National High Magnetic Field Laboratory; Estados Unidos