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QCMP017. MOPAC-PC: A Microcomputer Version of
MOPAC (A General Molecular Orbital Package)
(Version 4.0)
by Santiago Olivella, Departament de Química
OrgO(a,½)nica, Facultat de Química,
Universitat de Barcelona, Martí i Franqués 1,
08028 Barcelona, Catalonia, Spain
MOPAC-PC is a microcomputer version of
Stewart's MOPAC program (QCPE 455) with some
additional features. It is written in IBM
Professional FORTRAN-77 (PROFORT), version
1.00, and runs under MS-DOS (versions 2.1 or
more recent) on IBM-PC and compatible systems
with floating point math coprocessor. A 10
Mb hard disk, a 360 Kb floppy disk drive, and
at least 512 Kb of RAM are required.
The new features that MOPAC-PC incorporates
are:
(1) The new AM1 (Austin Model 1)1 Hamiltonian
is included. AM1 parameters are currently
available for C, H, O, N, F, Cl, Br, and I.
(2) The MNDO parameters for lithium are
included.2
(3) Four new key words (ALTER, ALTA, ALTB
and GUESS) are included. These key words may
be used to select a particular electronic
configuration inopen-shellsystem
calculations.
(4) The errors in the code of MOPAC (QCPE
455) that were giving rise to incorrect
results (i.e., energy partitioning in MINDO/3
calculations, localized eigenvectors, net
atomic charges and dipole moments in
calculations using key words BIRADICAL,
EXCITED, CI etc.) have been corrected.
In order to work on microcomputers with only
512 Kb of RAM, MOPAC-PC has been broken up
into four programs or executable modules,
each of which performs one of the four
general classes of calculations of the
original package. These are:
MOPAC1: Performs normal geometry
optimizations, reaction coordinate
calculations and "SADDLE" transition-state
searches.
MOPAC2:Performs geometry optimizations
using Bartel's Non-Linear Least-Squares
gradient norm minimization method (key word
NLLSQ).
MOPAC3:Performs geometry optimizations
using the McIver-Komornicki gradient norm
minimization method (key word SIGMA).
MOPAC4: Performs force-constant calculations
(key word FORCE), including vibrational
frequencies and thermodynamic quantities.
Note that, in microcomputers equipped with 1
Mb or more of RAM, the entire MOPAC-PC may be
assembled in one executable module. This
module would be similar in functionality to
the standard MOPAC executable image that runs
on VAX 11/780 minicomputers.
MOPAC-PC is distributed on two double-sided
diskettes of 360 Kb that contain the entire
source code (broken up by individual
subroutines, 91 in total), four sample input
data files and the output files that these
input files produce, and a file that is a
manual with the instructions on the use and
installation of the program.
Since any of the above-mentioned four
executable modules cannot be held in one 360
Kb floppy disk, these modules are not
contained in the MOPAC-PC distribution
diskettes. The user, therefore, must create
each one of the executable modules in the
microcomputer core memory and then save the
modules on the hard disk.
Note:The largest molecule which can be
dealt with in QCMP017 as QCPE
distributes it is 7 heavy atoms and 7
light atoms.
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References:
1. M.J.S. Dewar, E. G. Zoebisch, E. F.
Healy, J.J.P. Stewart, J. Am. Chem. Soc.,
107, 3902 (1985).
2.W. Thiel, personal communication
(January, 1982).
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FORTRAN 77 (IBM Professional FORTRAN)
Lines of Code: 13,000
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