Monte Carlo molecular modeling

About: Monte Carlo molecular modeling is a research topic. Over the lifetime, 11307 publications have been published within this topic receiving 409122 citations.

Methodological assessment of kinetic Monte Carlo simulations of organic photovoltaic devices: the treatment of electrostatic interactions.

Abstract: The kinetic Monte Carlo (KMC) method provides a versatile tool to investigate the mechanisms underlying photocurrent generation in nanostructured organic solar cells. Currently available algorithms can already support the development of more cost-efficient photovoltaic devices, but so far no attempt has been made to test the validity of some fundamental model assumptions and their impact on the simulation result. A meaningful example is given by the treatment of the electrostatic interactions. In most KMC models, electrostatic interactions are approximated by means of cutoff based potentials, irrespective of the long-range nature of the Coulomb interaction. In this paper, the reliability of such approximation is tested against the exact Ewald sum. The results under short-circuit and flat-band conditions show that use of cutoff-based potentials tends to underestimate real device performance, in terms of internal quantum efficiency and current density. Together with this important finding, we formalize other methodological aspects which have been scarcely discussed in the literature.

Molecular dynamics for discontinuous potentials

Abstract: A method to perform molecular dynamics simulations for systems of particles interacting with discontinuous potentials is presented. It is a generalization of Alder and Wainwright's algorithm for potentials represented by an arbitrary number of discontinuous horizontal line segments. The method is applied to several hard molecular fluids of various shapes, discrete Lennard-Jonesium, surfaces and mixtures in order to test its generality and flexibility. Results are compared, when possible, with previously published material, which includes numerical, theoretical and experimental results. These comparisons show that the method is a powerful tool in the study of molecular fluids and looks like a promising alternative approach to perform molecular dynamics for continuous potentials represented by a series of discontinuous line segments. The flexibility of the method will allow the testing of theories based on integral equations, like RISM and RAM, and to develop equations of state for complex hard molecules to...

Quantum Monte Carlo and variational approaches to the Holstein model

Abstract: Based on the canonical Lang-Firsov transformation of the Hamiltonian we develop a very efficient quantum Monte Carlo algorithm for the Holstein model with one electron. Separation of the fermionic degrees of freedom by a reweighting of the probability distribution leads to a dramatic reduction in computational effort. A principal component representation of the phonon degrees of freedom allows to sample completely uncorrelated phonon configurations. The combination of these elements enables us to perform efficient simulations for a wide range of temperature, phonon frequency, and electron-phonon coupling on clusters large enough to avoid finite-size effects. The algorithm is tested in one dimension and the data are compared with exact-diagonalization results and with existing work. Moreover, the ideas presented here can also be applied to the many-electron case. In the one-electron case considered here, the physics of the Holstein model can be described by a simple variational approach.