Characterization of a hybrid Monte Carlo search algorithm for structure determination

2005 ◽  
Vol 38 (1) ◽  
pp. 107-111 ◽  
Author(s):  
Anders J. Markvardsen ◽  
Kenneth Shankland ◽  
William I. F. David ◽  
Gareth Didlick
Keyword(s):  
Monte Carlo ◽  
Crystal Structures ◽  
Structure Determination ◽  
Search Algorithm ◽  
Time Frame ◽  
Control Parameters ◽  
Acta Cryst ◽  
Hybrid Monte Carlo ◽  
Monte Carlo Search ◽  
Reasonable Time Frame

A hybrid Monte Carlo (HMC) search algorithm has recently been shown to be a promising method for structure determination from powder diffraction data [Johnston, David, Markvardsen & Shankland (2002).Acta Cryst.A58, 441–447]. Here, the performance of the algorithm on a number of different crystal structures is investigated as a function of its control parameters. This detailed analysis required the use of a system for distributed computing in order to keep the calculation times within a reasonable time frame. The results obtained confirm previous findings and a detailed discussion of the effect of the control parameters on the efficiency of the HMC method is provided. The results suggest a method for setting these parameters automatically, which is an essential step if HMC is to find routine use in the determination of crystal structures.

Pauling’s rules guided Monte Carlo search (PAMCARS): A shortcut of predicting inorganic crystal structures

2020 ◽  
Vol 256 ◽  
pp. 107486
Author(s):  
Yang Zhong ◽  
Zhenpeng Hu ◽  
Tongqing Sun ◽  
Weiwei Wang ◽  
Yongfa Kong ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Crystal Structures ◽  
Inorganic Crystal ◽  
Monte Carlo Search

scholarly journals MONTE-CARLO EXPRESSION DISCOVERY

2013 ◽  
Vol 22 (01) ◽  
pp. 1250035 ◽  
Author(s):  
TRISTAN CAZENAVE
Keyword(s):  
Monte Carlo ◽  
Genetic Programming ◽  
Search Algorithm ◽  
Fitness Function ◽  
Benchmark Problems ◽  
Tree Search ◽  
Confidence Bounds ◽  
Local Optima ◽  
Monte Carlo Tree Search ◽  
Monte Carlo Search

Monte-Carlo Tree Search is a general search algorithm that gives good results in games. Genetic Programming evaluates and combines trees to discover expressions that maximize a given fitness function. In this paper Monte-Carlo Tree Search is used to generate expressions that are evaluated in the same way as in Genetic Programming. Monte-Carlo Tree Search is transformed in order to search expression trees rather than lists of moves. We compare Nested Monte-Carlo Search to UCT (Upper Confidence Bounds for Trees) for various problems. Monte-Carlo Tree Search achieves state of the art results on multiple benchmark problems. The proposed approach is simple to program, does not suffer from expression growth, has a natural restart strategy to avoid local optima and is extremely easy to parallelize.

The Monte Carlo method for finding missing atoms in solving crystal structures from powder diffraction data without applying a rigid-body approximation

2001 ◽  
Vol 16 (2) ◽  
pp. 65-70 ◽  
Author(s):  
Hisayoshi Nakamura ◽  
Satoru Yamazaki ◽  
Tomohiko Ohnishi ◽  
Takashi Ida ◽  
Hideo Toraya
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Rigid Body ◽  
Crystal Structures ◽  
Structural Information ◽  
Inorganic Crystal ◽  
The Monte Carlo Method ◽  
Structure Solution ◽  
Monte Carlo Search ◽  
Correct Structure

The Monte Carlo method is applied to finding missing atoms in solving inorganic crystal structures without applying a rigid-body approximation. Whole powder patterns of α-SiO2 and Mg2SiO4 were used for testing a procedure. Four atoms among the six in the asymmetric unit of Mg2SiO4 could be found in the present analysis. The use of well-refined profile parameters enhanced the frequency of correct structure configurations in the Monte Carlo search. Utilizing structural information available for constructing a trial configuration is also considered to be important for efficiently searching the structure solution. A procedure for assignment of equivalent positions to respective atoms is presented. The method can be used as a powerful tool for finding missing atoms in a partially solved structure. A histogram of weighted reliability index in Monte Carlo calculations is very informative for evaluating the performance of the method. ©

An enantiomerically pure P-stereogenic bisphosphine: (S,S)-ethylenebis[(2-methylphenyl)phenylphosphine] (o-tolyl-DiPAMP)

2014 ◽  
Vol 70 (12) ◽  
pp. 1174-1177
Author(s):  
Wioletta Bendzińska-Berus ◽  
Magdalena Kaik-King ◽  
Gary King ◽  
Urszula Rychlewska
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Research Program ◽  
Structure Determination ◽  
Title Compound ◽  
X Ray Diffraction ◽  
Acta Cryst ◽  
Enantiomerically Pure ◽  
X Ray

In connection with a research program involving the synthesis, structure determination, reactivity and ability to coordinate to metal centres of chiral bisphosphine ligands, we have synthesized and structurally characterized, by means of single-crystal X-ray diffraction analysis, the title compound {systematic name: (S,S)-(ethane-1,2-diyl)bis[(2-methylphenyl)phenylphosphane], abbreviated aso-tolyl-DiPAMP}, C28H28P2. So far, neither the free bisphosphine (DiPAMP) nor analogues that incorporate the ethylenebisphosphine frame have had their crystal structures reported. The investigated compound forms crystals which are isostructural with the bisphosphine dioxide analogue [Kinget al.(2007).Acta Cryst.E63, o3278], despite the involvement of the dioxide in C—H...O(=P) hydrogen bonds and the lack of similar hydrogen bonds in the investigated crystal structure. In both molecules, the P—C—C—P chain is in atransconformation, extended further at both ends by one of the two P—Cipsobonds. The planes of the phenyl ando-tolyl rings attached to the same P atom are nearly perpendicular to one another. Both crystal structures are mainly stabilized by dispersive interactions.

scholarly journals Monte Carlo Search Algorithm Discovery for Single-Player Games

2013 ◽  
Vol 5 (3) ◽  
pp. 201-213 ◽  
Author(s):  
Francis Maes ◽  
David Lupien St-Pierre ◽  
Damien Ernst
Keyword(s):  
Monte Carlo ◽  
Search Algorithm ◽  
Monte Carlo Search
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