CRYSTAL program system

The program system COBRA [118, 119] can be regarded as a rule- and data-based approach, but also applies the principles of fragment-based (or template-based) methods extensively (for a detailed description sec Chapter 11, Sections 7.1 and 7.2 in the Handbook). COBRA uses a library of predefined, optimized 3D molecular fragments which have been derived from crystal structures and foi ce-field calculations. Each fi agment contains some additional information on... 

Structural constitution on a submicron scale as related to crystallinity, viz., crystalline unit cells, lamellae shape and size, and stress-induced shish kebab crystals. Computer system that stores, analyzes, and adjusts the controls of a machine based on the parameters established during the operation of the machine it is controlling. It continuously analyzes output data to adjust and maintain the machine s cycle within programmed limits. Can also store data and output it as directed by programming. 

From the diffraction pattern, the crystal structure can be determined mathematically and the compound identified. While the discussion of the details is beyond the scope of this text, small, benchtop automated single-crystal XRD systems have come into use. These instruments possess a variety of powerful data processing programs and libraries that permit the determination of high-resolution crystal structures of small molecules rapidly and automatically. Systems include the Rigaku XtaLAB mini and the Bruker X2S. 

P. T. Beurskens et al.. DIRDIF, a Computer Program System for Crystal Structure Determination by Patterson Methods and Direct Methods applied to Difference Structure Factors. 1992. 

Crystal (we tested Crystal 98 1.0) is a program for ah initio molecular and band-structure calculations. Band-structure calculations can be done for systems that are periodic in one, two, or three dimensions. A separate script, called LoptCG, is available to perform optimizations of geometry or basis sets. 

Table X gives an idea of the strength of the various expansion methods, and it shows that, by using the principal term only, one can hardly expect to reach even the above-mentioned chemical margin, even if the wave function W gO(D) is actually very close in the helium case. This means that one has to rely on expansions in complete sets, and the construction of the modern electronic computers has fortunately greatly facilitated the numerical solution of secular equations of high order and the calculation of the matrix elements involved. For atoms, the development will probably go very fast, but, for small molecules one has first to program the conventional Hartree-Fock scheme in a fully self-consistent way for the computers, before the next step can be taken. For large molecules and crystals, the entire situation is much more complicated, and it will hence probably take a rather long time before one can hope to get a detailed understanding of the correlation phenomena in these systems.

NC samples were irradiated for 3 min and TNT and HMX for 1 min at a 14 MeV neutron flux of approx 108n/cmasec, Simultaneous counting was performed by means of a matched dual 7.6x7.6cm flat Nal crystal detector assembly in conjunction with a Kaman Nuclear programmed timer system for automatic sample transfer, A one-min count time was usually sufficient to exceed 10 counts. The signal from each de-... 

Crystal structures of the NS5B polymerase alone and in complexes with nucleotide substrates have been solved and applied to discovery programs (Ago et al. 1999 Bressanelli et al. 2002 Bressanelli et al. 1999 Lesburg et al. 1999 O Farrell et al. 2003). From these studies, HCV polymerase reveals a three-dimensional structure that resembles aright hand with characteristic fingers, palm, and thumb domain, similar to the architectures of the RNA polymerases of other viruses. However, none of these experimental structures contained the ternary initiation complex with nu-cleotide/primer/template, as obtained with HIV RT. Accordingly, HCV initiation models have been built using data from other viral systems in efforts to explain SAR (Kozlov et al. 2006 Yan et al. 2007). 

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