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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
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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
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a10 MHz 80286 host WC286; bwith floating
point accelerator; cwithout optimization
option; dwith standard optimization option.
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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
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