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Inorganic Crystal Structure Database (inorganic + crystal_structure_database)
Selected AbstractsNovel Approach for Clustering Zeolite Crystal StructuresMOLECULAR INFORMATICS, Issue 4 2010M. Lach-hab Abstract Informatics approaches play an increasingly important role in the design of new materials. In this work we apply unsupervised statistical learning for identifying four framework-type attractors of zeolite crystals in which several of the zeolite framework types are grouped together. Zeolites belonging to these super-classes manifest important topological, chemical and physical similarities. The zeolites form clusters located around four core framework types: LTA, FAU, MFI and the combination of EDI, HEU, LTL and LAU. Clustering is performed in a 9-dimensional space of attributes that reflect topological, chemical and physical properties for each individual zeolite crystalline structure. The implemented machine learning approach relies on hierarchical top-down clustering approach and the expectation maximization method. The model is trained and tested on ten partially independent data sets from the FIZ/NIST Inorganic Crystal Structure Database [source] On symmetry classes of crystal structuresACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2009Hans Burzlaff An open-ended classification scheme for crystal structures based on Wyckoff sets and affine normalizer groups is proposed. It is free of metrical and geometrical considerations. All structures of one structure type belong to the same symmetry class. An application is given for the Inorganic Crystal Structure Database (version 2, 2007). [source] An investigation into structural changes due to deuterationACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2008S. J. Fisher Perdeuteration of proteins is becoming more commonplace and the assumption is in general that deuteration does not affect protein structure. In this work, the effect of deuteration on structure is examined by data mining, largely of the Cambridge Structural Database but also of the Inorganic Crystal Structure Database, for deuterated and hydrogenated pairs of small-molecule structures analysed by neutron and X-ray crystallography. Differences between these small-molecule structures have been calculated and the results thus far follow the initial assumption. However, functional changes are known, e.g. D2O is toxic to living systems but H2O is not, kinetics change, small pH to pD changes occur, proteins stiffen in D2O and ferroelectrics alter their properties. [source] Ln3M1,,,,TX7, quasi-isostructural compounds: stereochemistry and silver-ion motion in the Ln3Ag1,,,,GeS7 (Ln = La,Nd, Sm, Gd,Er and Y; , = 0.11,0.50) compoundsACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2009Marek Daszkiewicz The crystal structures of the Ln3Ag1,,,,GeS7 (Ln = La,Nd, Sm, Gd,Er, Y; , = 0.11,0.50, space group P63) compounds were determined by means of X-ray single-crystal diffraction and the similarities among the crystal structures of all Ln3M1,,,,TX7 (space group P63; Ln , lanthanide element, M, monovalent element; T, tetravalent element and X, S, Se) compounds deposited in the Inorganic Crystal Structure Database (ICSD) are discussed. Substitutions of each element in Ln3M1,,,,TX7 result in a different structural effect. On the basis of the data deposited in the ICSD the large family of the Ln3M1,,,,TX7 compounds was divided into three groups depending on the position of the monovalent element in the lattice. This position determines what kind of stereoisomer is present in the structure, either the ++ enantiomer or the +, diastereoisomer. Since the silver ions can occupy a different position and the energy barriers between positions are low the ions can move through the channel. It was shown that this movement is not a stochastic process but a correlated one. [source] Bond analyses of borates from the Inorganic Crystal Structure DatabaseACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2006Daqiu Yu Various fundamental building blocks (FBBs) are observed in the crystallographic structures of oxoborates available in the Inorganic Crystal Structure Database, Version 1.3.3 (2004); the occurrence of borate groups with low complexity is dominant. Bond-valence parameters d0 of B,O bonds in 758 oxoborates with various FBBs have been calculated using the bond-valence sum model. Some discrepancies in the d0 values obviously occur if the detailed configurations of FBBs in borate crystals are considered; d0 is sensitive to the chemical bonding structure of B atoms in the crystallographic framework. Moreover, d0 values are affected by the existence of interstitial atoms and the substitution of other anionic groups. In addition, the d0 parameters for B,N, B,S, B,P and B,F bonds are also calculated statistically. Some suitable d0 data for various borate FBBs are recommended according to their particular configurations, especially for those with low complexity. On the basis of the proposed linear relationship between calculated nonlinear optical (NLO) coefficients of borates and the current d0 values for various FBBs, it is found that the d0 values may be regarded as a useful parameter for pre-investigating the NLO properties of borates, leading to an efficient structural evaluation and design of novel borates. [source] Systematic prediction of new ferroelectrics in space groups P31 and P32ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2003S. C. Abrahams Release 2002/2 of the Inorganic Crystal Structure Database (FIZ Karlsruhe, Germany, and Institute Laue,Langevin, Grenoble, France) contains 62 entries in space group P31 and ten entries in space group P32 for 49 different materials including eight families with two or more isostructural members. The structural criteria for ferroelectricity are satisfied for 16 new structure types at a confidence level that depends on the reliability of each determination. LaBGeO5, a mineral with stillwellite structure, was previously reported as ferroelectric and forms an additional family with seven other members or related structures that satisfy the criteria. Ten structures reported in space group P31 or P32 are dubious or incorrect, with atomic coordinates that satisfy supergroup symmetry. One material is probably pyroelectric but is unlikely to become ferroelectric, and three others are either incompletely solved or incompletely refined. Among the predicted new ferroelectrics are Cu2BaGeS4, Fe3(Fe,Si)O4(OH)5, Se4S5, K2HCr2AsO10, IV-RbNO3, Rb2Sc(NO3)5, Na3ReO5, Nd14(GeO4)2(BO3)6O8, CsHgCl3, Ba2Cu2AlF11, KYF4, SrS2O6·4H2O, Cu3PbTeO6(OH)2, ReH(CO)4, Ni2(NH3)9Mo(CN)8·2H2O and the 6T polytype of Ca1.89Ta1.80Sm0.16Ti0.10O7, in addition to ,-LaBSiO5, PbBAsO5 and BaBAsO5 in the stillwellite family. [source] Prediction of new displacive ferroelectrics through systematic pseudosymmetry search.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2002Pmc21 symmetry, Results for materials with Pba Polar structures with pseudosymmetry related to a hypothetical non-polar configuration are considered as good candidates for ferroelectrics. Recently, a procedure has been developed for a systematic pseudosymmetry search among structures with a given space-group symmetry. The aim of this paper is the extension of the pseudosymmetry procedure to the case of structures with polar symmetry and its application in the search for new ferroelectrics. The results obtained by the generalized pseudosymmetry search among the compounds with symmetries and listed in the Inorganic Crystal Structure Database are discussed. The calculations have been performed by the program PSEUDO, which forms part of the Bilbao Crystallographic Server (http://www.cryst.ehu.es). In addition, an empirical relation between the atomic displacements necessary to reach the non-polar structure and the transition temperature is proposed and compared with the Abrahams,Kurtz,Jamieson relation. [source] Application of graph theory to detect disconnected structures in a crystallographic database: copper oxide perovskites as a case studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2000Yuri Kotliarov Every crystal structure can be described as a graph with atoms as vertices and bonds as edges. Although such a graph loses the space arrangement of atoms and symmetry elements, it can mathematically represent the connectivity between atoms. This topological approach was used to develop a new method for detecting disconnected structures, in which individual atoms or structural fragments are located too far from each other, forming impossibly large gaps. Approximately 2300 perovskite-related crystal structures have been extracted from the Inorganic Crystal Structure Database (in 1999) and the maximum disconnecting distances, and the relations between them and the ionic radii of elements, have been analysed. Several disconnected structures, which are erroneous by our definition, have been revealed. Conventional tests for crystallographic data checking did not detect those entries. [source] | ||||||||||