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QCMP035. BIGSTRN-3: General-Purpose Force Field
Program (IBM-PC/DSI32 Version)
Modified by Andrzej B. Buda, Princeton
University, Department of Chemistry,
Princeton, New Jersey 08544, after Robert B.
Nachbar, Merck Sharp & Dohme Research
Laboratories, Rahway, New Jersey 07065 and
Kurt Mislow, Department of Chemistry,
Princeton University, Princeton, New Jersey
08544
BIGSTRN-3 is a general-purpose program for empirical force-field (EFF) calculations. Although its main goal is to optimize molecular geometry, it is also capable of locating the geometry of the transition states.Moreover, there are built-in features which describe the nature of the located structure (minimum, transition state or partial maximum) and also elucidate the symmetry of the stationary points. However, the program is slower than other EFF programs (particularly MM21) partially due to the double precision of its variables and FORTRAN intrinsic functions (MM2 uses single precision) and partially due to the nature of the optimization procedures and its high precision convergence criteria. Nevertheless, BIGSTRN-3 is a powerful and indispensable tool for theoretical static and dynamic sterochemistry. The DSI-32/22 board is one of several boards with 32-bit processors available for IBM- PC/AT computers. The DSI-32/2 card carries a 10 MHz National Semiconductor 32032 32-bits processor, a 32081 floating point coprocessor, and contains 2 Mb of linear addressing memory (which can be extended up to 8 Mb). The DSI-32 version of BIGSTRN-3 is a full edition of the VAX version (QCPE 514), except that the molecular geometry can be read either in original BIGSTRN-3 format or MM2(85) format. Several changes had to be made in the I/O routines and in the timing and date procedures as well. The package contains 25000 lines of code split over l35 FORTRAN subroutines and functions and four data files with four empirical force-field parameters (MM2, Andose-Mislow, Engler- Andose-Schleyer and Ermer-Lifson).The FORTRAN code of BIGSTRN-3 occupies 567 Kb. The executable version (compiled with DSI Green-Hills FORTRAN77 compiler and linked with LINKER) needs 1.56 Mb of space on the disk and uses 95% of the 2 Mb DSI-32 core memory. The benchmark calculations for several molecules using DSI-32/2 board and VAX computers are shown in Table 1. System requirements: 1. IBM-PC, XT or AT with 128 Kb of RAM 2. 20 Mb (or larger) hard disk 3. 350 Kb or 1.2 Mb floppy disk 4. DOS 2.xx or higher 5. DSI-32/2 coprocessor board 6. DSI-32 operating system 7. DSI/Green-Hills FORTRAN 77 compiler __________ TABLE 1. The calculation time (in sec.) for benzene and cyclooctene (COTE) geometry optimization. For VAX 11/780 MicroVAX, the CPU time is given, whereas for the IBM-AT compatible Western Computer 286 Turbo (WC286) with DSI-32/2 card, the realtime of calculations is shown (output displayed on the screen). Computer Operating System Compiler Time benzene COTE WC286a DSI-32/2 PC-DOS 3.20 DSI/GH FORTRAN 196.4 579.4 MicroVAXbVMS 4.4VAX FORTRANd 54.8 186.5 VAX 11/780VMS 4.4VAX FORTRANd 42.7 140.0 __________ a10 MHz 80286 host WC286; bwith floating point accelerator; cwithout optimization option; dwith standard optimization option. _________ References: 1 N. L. Allinger, J. Am. Chem. Soc., 99, 8127 (1977). 2 More information about DSI-32 boards may be obtained from: Definicon Systems Inc. 31324 Via Colinas Suite 108 Westlake Village, CA 91362 FORTRAN 77 (Microsoft FORTRAN) Lines of Code: 25000 |