Reverse Monte Carlo modeling

INVESTIGATION OF THE STRUCTURAL DISORDER D4 ICE Ih USING NEUTRON DIFFRACTION AND REVERSE MONTE CARLO MODELLING... 

RMCPOW RMCA Version 3, R. L. McGreevy, M. A. Howe and J. D.Wicks, (1993), available at http // www.studsvik.uu.se/ and Reverse Monte Carlo modelling of neutron powder diffraction data, A. Mellergard and R. L. McGreevy, Acta Crystallogr., Sect. A, 1999, 55, 783 Direct Space for magnetic structures... 

RMC Reverse Monte Carlo modelling of neutron powder diffraction... 

RMC + + G. Evrard, L. Pusztai, Reverse Monte Carlo Modelling of the... 

Petersen, T., Yarovsky, 1., Snook, 1., et al. (2004). Microstructure of an industrial char by diffraction techniques and Reverse Monte Carlo modelling. Carbon, 42, 2457-69. 

Given a model obtained by reverse Monte-Carlo modeling. 

Unfortunately, there are no suitable isotopes for each element good elements are, for instance, chlorine and nickel. In many cases, differences between coefficients are not big enough for the matrix inversion i.e., the set of equations is ill defined. Sometimes, application of the Reverse Monte Carlo modeling method can help in separating partial structure... 

Soyer-Uzun S., Benmore C.)., Siewenie J. E., and Sen S., The nature of intermediate-range order in Ge-As-S glasses results from Reverse Monte Carlo modeling,/. Phys. Condens. Matter, 22,115404 (9 pages) (2010). 

Timoshenko J., Kuzmin A., and Purans J., Reverse Monte Carlo Modeling of thermal disorder in crystalline materials from EXAFS spectra. Com. Phys. Comm., 183,1237-1245 (2012). 

Abe, H. (2007b) Reverse Monte Carlo Modeling of Local Structure Using Short-Range and Medium-Range Order Parameters,. Phys. Soc. jm. Vol. 76 094601-6. 

In all these examples, the importance of good simulation and modeling cannot be stressed enough. A variety of methods have been used in this field to simulate the data in the cases studies described above. Blander et al. [4], for example, used a semi-empirical molecular orbital method, MNDO, to calculate the geometries of the free haloaluminate ions and used these as a basis for the modeling of the data by the RPSU model [12]. Badyal et al. [6] used reverse Monte Carlo simulations, whereas Bowron et al. [11] simulated the neutron data from [MMIM]C1 with the Empirical Potential Structure Refinement (EPSR) model [13]. 

Random structure methods have proved useful in solving structures from X-ray powder diffraction patterns. The unit cell can usually be found from these patterns, but the normal single-crystal techniques for solving the structure cannot be used. A variation on this technique, the reverse Monte Carlo method, includes in the cost function the difference between the observed powder diffraction pattern and the powder pattern calculated from the model (McGreevy 1997). It is, however, always necessary to include some chemical information if the correct structure is to be found. Various constraints can be added to the cost function, such as target coordination numbers or the deviation between the bond valence sum and atomic valence (Adams and Swenson 2000b Swenson and Adams 2001). 

McGreevy, R. L. (1997). Reverse Monte Carlo methods for structure modelling. In C. R. A. Catlow (ed.), Computer Modelling in Inorganic Crystallography. San Diego and New York Academic Press, pp. 151-84. 

Swenson, J. and Adams, St. (2001). The application of the bond valence method to reverse Monte Carlo produced structural models of superionic glasses. Phys. Rev. B64, 024204. 

This paper does not intend to be a review rather comments and examples are given for some of the recent progress. The related literature is not searched exhaustively and the selection is rather arbitrary. Preliminary results of two new studies by the XD method are presented in order to demonstrate the capabilities of the method at new conditions. The reverse Monte Carlo (RMC) technique is also discussed in more detail to show a new perspective in the structural modelling of solutions. 

The main advance in recent years has been the development of methods to obtain models of structures that are consistent with the total diffraction pattern. One method is the Reverse Monte Carlo (RMC) method (McGreevy and Pusztai 1988, McGreevy 1995, Keen 1997, 1998). In this method, the Monte Carlo technique is used to modify a configuration of atoms in order to give the best agreement with the data. This can be carried out using either S Q) or T(r) data, or both simultaneously. We also impose a... 

ARITVE Modelling the Silica Glass Structure by the Rietveld Method. A. Le Bail, J. Non Cryst. Solids, 1995, 183, 39 42, and Reverse Monte Carlo and Rietveld Modelling of the NaPbM2F9 (M = Fe, V) Fluoride Glass Structures, A. Le Bail, J. Non Cryst. Solids, 2000, 271, 249 259... 

Thompson, K.T. and Gubbins, K.E. (2000). Modeling structural morphology of microporous carbons by reverse Monte Carlo. Langmuir, 16, 5761—73. 

The goal of reconstruction methods is to build model pore structures that match experimental structure data (including surface chemistry data) for the real materials, at least in a quafitative way. For example, models can be constructed that match the experimental structure factor, S(q), or TEM data, by reverse Monte Carlo (RMC), off-lattice reconstruction, or other methods. 

Pikunic, J., Clinard, C., Cohaut, N., et al. (2003). Structural modeling of porous carbons constrained reverse Monte Carlo method. Langmuir, 19, 8565-82. 

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