A core strength of the Theoretical Chemical and Quantum Physics Group

Outline

The Hybrid Reverse Monte Carlo method is a fitting routine which aims to produce three dimensional atomic coordinates of disordered materials which are consistent with a variety of experimental data while ensuring a low energy local bonding environment. Experimental data may include electron, x-ray and neutron diffraction, EXAFS and porosity information.

The HRMC methodology was developed to address two critical shortcomings in two fields employing the Metropolis-Hastings algorithm.

  • Traditional energy minimizing Metropolis Monte Carlo (MMC) method which produces atomic configurations by minimizing an empirical potential energy function. This methodology lacks a direct connection to experimental data.
  • The Reverse Monte Carlo (RMC) method which fits only experimental data such as the radial distribution function G(r) or structure factor S(q). This methodology tends to produce unphysical local bonding environments for materials that have significant bond angle dependence.

The HRMC method addresses both issues by simultaneously minimizing the potential energy as well as the discrepancy between simulation and experimental data. This methodology was pioneered within our group.

A comparison of HRMC and RMC

A comparison of HRMC (left) and RMC (right) resulting structures for amorphous carbon. While both configurations are consistent with experimental diffraction data, the RMC local bonding environment is physically unrealistic. The empirical potential in HRMC ensures that the bond angles are realistic.

Recent Publicatios

G. Opletal, T. Petersen, B. O'Malley, I. Snook, D. G. McCulloch, N. A. Marks and I. Yarovsky, Hybrid approach for generating realistic amorphous carbon structures using metropolis and reverse Monte Carlo, Mol. Sim. 28, 927 (2002)

T. Petersen, I. Yarovsky, I. Snook, D. G. McCulloch and G. Opletal, Structural analysis of carbonaceous solids using an adapted reverse Monte Carlo algorithm, Carbon 41, 2403 (2003)

T. Petersen, I. Yarovsky, I. Snook, D. G. McCulloch and G. Opletal, Microstructure of an industrial char by diffraction techniques and a Reverse Monte Carlo modeling, Carbon 42, 2457 (2004)

G. Opletal, T. C. Petersen, D. G. McCulloch, I. K. Snook and I. Yarovsky, The structure of disordered carbon solids studied using a hybrid reverse Monte Carlo algorithm, J. Phys.: Condens. Matter 17, 2605 (2005)

G. Opletal, T. C. Petersen, I. K. Snook and D. G. McCulloch, Modeling of structure and porosity in amorphous silicon systems using Monte Carlo methods, J. Chem. Phys. 126, 214705 (2007)

G. Opletal, T. C. Petersen, B. O'Malley, I. K. Snook, D. G. McCulloch and I. Yarovsky, HRMC: Hybrid Reverse Monte Carlo method with silicon and carbon potentials, Comp. Phys. Comm. 178, 777 (2008)


For more information about this technique, please contact George Opletal or visit http://www.hrmccode.com