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COMPUTER PROGRAM ABSTRACTS
Computer Program Abstracts The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and signi®cant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr Commission on Crystallographic Computing. It should not exceed 500 words in length and should follow the standard format given on page 189 of the June 1985 issue of the Journal [J. Appl. Cryst. (1985). 18, 189± 190] and on the World Wide Web at http://www.iucr. org/journals/jac/software/. Lists of software presented and/or reviewed in the Journal of Applied Crystallography are available on the World Wide Web at the above address, together with information about the availability of the software where this is known.
J. Appl. Cryst. (1998). 31, 972
NOPTSUS ± a program for computing nonlinear-optical susceptibilities from structure data CH. SCHETELICH Physics Department, University of Warwick, Coventry CV4 7AL, England. E-mail:
[email protected] (Received 2 February 1998; accepted 12 February 1998 )
The crystallographic problem: As a result of better and more ef®cient nonlinear-optical (NLO) materials used, for example, as frequency doublers, the search for crystals showing large second-harmonic-generation (SHG) coef®cients has been extended to many more compounds. However, the problem is that there is no reliable way to predict the nonlinear properties of these compounds and therefore the only method is to grow crystals and measure their properties. This is mostly a timeconsuming and very expensive solution. To avoid this problem, different theoretical approaches have been developed. One of these is the bond-charge model of Levine (1973a,b,c). His semiempirical description uses crystal structural data together with a set of predetermined empirical parameters to calculate the nonlinear susceptibilities. The nonlinear susceptibilities are obtained by the computation of a (macroscopic) susceptibility for each bond, followed by a summation over all bonds in the unit cell. In the original work, the model was applied only to comparatively simple structures. To undertake a more systematic investigation of the in¯uence of the different parameters as well as the application of the model to a much wider range of structures, the program presented here has been written. # 1998 International Union of Crystallography Printed in Great Britain ± all rights reserved
Method of solution: To use the program, an input ®le has to be generated consisting of a header (title, crystal system, lattice parameters, formula units per unit cell) and a list of atomic coordinates and bond properties (type, constituents, bond length). This can be done manually or using the ATOMS program written by Eric Dowley. From the input ®le, a list of bonds belonging to the unit cell is created. The required chemical information about the atoms forming the bonds, i.e. core charge, coordination number, stoichiometry, atomic radius, and the speci®c character of the atom (transition or noble metal etc.), can then be ®lled in using the bond parameters of the options menu. After this, the ®le is saved and the input data are ready for use. The calculation output consists of several data sheets for the different bond types and a summary for the whole crystal. The output includes all model parameters of interest, the geometrical factors describing the arrangements of the bond, the tensor components for the nonlinear susceptibility and Miller's delta. By a subsequent adjustment of the values of the bond parameters in the options menu, the effect of the different parameters on the nonlinear susceptibility can be studied. Software and hardware environment: The program is written in Borland Pascal for Windows (V.7.0) and has been compiled for DOS/WINDOWS PCs. It runs well on a 486/33 MHz computer with 4 Mbytes of RAM. The program is equipped with a graphical interface and the use of a mouse pointer is recommended. Program speci®cation: The compiled code has a size of 300 kbytes; the size of the input ®les (.dta and .atd ®les) varies between 5 and 100 kbytes. The conversion of input ®les to the programspeci®c format can take 30±80 s depending on the ®le size. The computation of the susceptibilities is usually carried out within a couple of seconds. Documentation and availability: The program comes with short online help as well as a sample input ®le. The compiled program, source code and a couple of sample input ®les (both .dta and .atd) are available via anonymous ftp from pope.phys.warwick.ac.uk in directory /pub/noprsus or by e-mail from the author. Keywords: nonlinear susceptibility; Miller's delta; bond-charge theory.
References Levine, B. F. (1973a). J. Chem. Phys. 59, 1463. Levine, B. F. (1973b). Phys. Rev. B, 7, 2600. Levine, B. F. (1973c). Phys. Rev. B, 7, 2591. J. Appl. Cryst. (1998). 31, 972±973
PINCER: a portable dataacquisition program based on a command language interpreter M. C. MILLER ,a* G. OSZLANYI ,b K. S. ACKROYD ,a C. MARSHALL ,a S. P. COLLINS ,a D. LAUNDYa AND R. J. CERNIK a a CLRC Daresbury Laboratory, Warrington WA4 4AD, England, and b KFKI Research Institute for Solid State Physics, H-1525 Budapest 114 POB 49, Hungary. E-mail:
[email protected]
(Received 24 May 1997; accepted 21 July 1997 )
The crystallographic problem: The acquisition of raw experimental data requires suf®cient ¯exibility to support an increasing diversity of techniques and instrumentation, often at very short notice. However, control-program modi®cations usually cannot keep pace because of software complexity. In addition, when attractive new computer platforms become available, the software may be so system speci®c that it is impractical to port it. Method of solution: PINCER provides ¯exibility, extensibility and portability both for users and maintainers. A command language interpreter (CLI) provides a tool kit of portable dataacquisition and support functions that can be invoked interactively or via macro command ®les. Internal variable handling, screen and ®le input/output (i/o), maths, hardware i/o, graphics and ¯ow control are included. By the combination of these functions in macros, novel experiments can be brought on-line very rapidly, as described by Tang, Miller, Clark, Player & Craib (1996). Internally, the modular structure and hardware abstraction allow new hardcoded instrument types to be added easily. Low-level i/o for major hardware interfaces permits new instruments to be rapidly connected interactively. Nearly all the source code is portable down to the device i/o level. Further Journal of Applied Crystallography ISSN 0021-8898 # 1998
COMPUTER PROGRAM ABSTRACTS
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information is given by Miller, Ackroyd & Oszlanyi (1994). The PD macro set exists for powder diffraction and general control as detailed by Tang, Miller & Laundy (1996), 4CIRCLE for single-crystal diffraction and CLAM for virtual instruments.
Tang, C., Miller, M. & Laundy, D. (1996). CLRC Technical Report DL-TR-96003. Daresbury Laboratory, Warrington, England.
Hardware environment: The diagrams can be viewed on any platform supporting a WWW browser with a VRML viewer plug-in. Stored on a hard-disk drive, the 80 ®les use 65 Mbytes of space.
J. Appl. Cryst. (1998). 31, 973
Software environment: MS-DOS and MS-Windows 3.1/95 are the main target platforms, plus a single Microware OS-9 version. Central development and maintenance is carried out under Unix. The program is coded in ANSI C. The Microsoft Visual C/C++ compiler is used together with National Instruments LabWindows/CVI for the enhanced Windows version.
VRML general position/ symmetry diagrams of the 80 layer groups
Program speci®cations: The diagrams are stored on a hard disk and loaded individually into a web browser and viewed with a VRML viewer plug-in.
Hardware environment: Most systems are of ISA/PCI bus PC type controlling a growing number of CAMAC, GPIB, RS232, Harwell 6000 and BEDE MINICAM instruments. A Motorola MVME147 processor hosts the single OS-9 system. Support for VMEbus instrumentation is planned. Development Unix PINCER versions run on SG Irix and Sun Solaris workstations. Program speci®cation: The command interpreter overhead per instruction is less than 0.5 ms on a Viglen 4DX33 PC running Windows 95. The program occupies 350 kbytes of memory at run-time except for the Labwindows version where the user interface and run-time library increase it to 3 Mbytes. It contains 40 000 lines of C source code, invoking hardware and graphics libraries. The macros contain more than 16 000 lines. Macros are available to provide a number of test cases for all CLI commands. Documentation: A user guide, system guide and primer are available in MSWord format and HTML (http:// www.dl.ac.uk/SRS/XRD/Pincer.dir). Online help is provided by the CLI and macros. Availability: Executables and macros can be obtained from the main author for academic use. Keywords: data acquisition; control; instrumentation; PC; command interpreter. References Tang, C. C., Miller, M. C., Clark, S. M., Player, M. A. & Craib, G. R. G. (1996). J. Synchrotron Rad. 3, 6±13. Miller, M. C., Ackroyd, K. S. & Oszlanyi, G. (1994). Daresbury Preprint DL/ CSE/P29E. Daresbury Laboratory, Warrington, England. # 1998 International Union of Crystallography Printed in Great Britain ± all rights reserved
DAVID K. TSHUDY B. LITVIN *
AND
DANIEL
Department of Physics, Penn State Berks±Lehigh Valley College, The Pennsylvania State University, PO Box 7009, Reading, PA 19610-6009, USA. E-mail:
[email protected] (Received 27 May 1998; accepted 24 July 1998 )
The crystallographic problem: The standard representations of the general position and symmetry diagrams of three-dimensional groups are twodimensional diagrams. These are projections onto a plane of, respectively, the general positions and the symbols of the symmetry elements. This is the case for space groups (International Tables for Crystallography, 1995) and for layer groups (Weber, 1929; Wood, 1964; Chapuis, 1996; Grell et al., 1988; International Tables for Crystallography, 1999). Three-dimensional diagrams of only the general position diagrams of the layer groups have been produced by Litvin & Litvin (1993). With this new program we have incorporated both the general position and symmetry diagrams into one three-dimensional diagram for each layer group. Each diagram can be rotated and zoomed to aid the visualization of the general positions and the symmetry of the 80 layer groups. Method of solution: The three-dimensional diagrams were developed using a commercial product (WalkThrough Pro by Virtus Corporation) and converted into VRML format. The general positions are represented by spheres and threedimensional symbols were introduced and used to represent the symmetry elements. Software environment: Needed to view the diagrams are a World Wide Web (WWW) browser with a VRML viewer plug-in, for example, Netscape with Cosmo, both widely available on the internet. Each diagram is individually loaded from hard disk and viewed within the browser.
Documentation: A symbol ®le lists the sequential numbering and symbols of the 80 layer groups and the symbols used to represent the positions and symmetry elements. Availability: Zipped ®les of the 80 diagrams and an Adobe Acrobat readable symbol ®le containing the documentation can be downloaded from http://www.bk.psu.edu/faculty/litvin. Alternatively, these ®les can be obtained by sending three formatted 1.44 Mbyte 3.500 disks to the correspondence author (DBL). Nonzipped ®les can be obtained by sending a single 100 Mbyte ZIP disk to the correspondence author. Keywords: layer groups; general position diagrams; symmetry diagrams; VRML; three-dimensional visualization. This work was supported by the National Science Foundation through grant Nos. DMR-9510335 and DMR9722799. References Chapuis, G. (1996). Diplomarbeit, Univ. of Zurich, Switzerland (unpublished). Grell, H., Krause, C. & Grell, J. (1988). Tables of the 80 Plane Space Groups in Three Dimensions. Berlin: Akademie der Wissenschaften der DDR. International Tables for Crystallography (1995). Vol. A. Dordrecht: Kluwer Academic Publishers. International Tables for Crystallography (1999). Vol. E. Dordrecht: Kluwer Academic Publishers. In the press. Litvin, S. Y. & Litvin, D. B. (1993). J. Appl. Cryst. 26, 498. Weber, L. (1929). Z. Kristallogr. 70, 309±327. Wood, E. A. (1964). The 80 Diperiodic Groups in Three Dimensions. Bell Telephone Technical Publications, Monograph 4680.
Crystallographers J. Appl. Cryst. (1998). 31, 973±974 The Royal Swedish Academy of Sciences has awarded the 1998 Gregori Aminoff prize, given for pioneering work in crystallography, to Aloysio Janner, Ted Janssen and Pieter Maarten de Journal of Applied Crystallography ISSN 0021-8898 # 1998
