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495. MOSOL: MOPAC for Solid-State Physics
by James J. P. Stewart, Frank J. Seiler Research Laboratory, U.S. Air Force Academy, Colorado 80840 MOSOL is designed to handle any crystalline solid system involving those elements parameterized for the MNDO (Modified Neglect of Differential Overlap) method. Currently, these include H, Be, B, C, N, O, F, Al, Si, P, S, Cl, Ge, Br, Sn, and I. Since MOSOL was designed to be as similar as possible to MOPAC, most of the facilities of MOPAC will eventually be made available in MOSOL. At the present time, only a very limited set of facilities (such as the basic geometry optimization and force calculations options) are provided. Other more time-consuming or computationally difficult facilities (such as gradient minimization, UHF calculations and reaction path-following options) are not yet written. Since solid-state theory involves many concepts in physics not present in molecular chemistry, a complete extra section designed to make use of these concepts has been written. Facilities provided here include graphical depiction of band-structure diagrams and the density of states (limited at present to one- dimensional systems). The most frequently used sequence of operations would involve the following steps: 1. A guessed unit cell and translation vectors would be geometry optimized. This is a slow step, and restart facilities are provided. 2. At the energy minimum, the SCF-Fock matrix and final geometry are output, preparatory to running the interactive package. 3. The interactive graphics package is run "on- line" to provide band structures and densities of states. There is no restriction on the space-group of the crystal nor on the point-group of the unit cell. MOSOL does not use symmetry unless explicitly requested to do so by the user. Weak intermolecular bonds, such as exist in crystalline benzene, can be handled, as well as extended molecular crystals such as diamond and boron nitride. As MOSOL makes use of the MNDO Hamiltonian, any types of system for which MNDO works well will also work well in MOSOL; conversely, any systems for which MNDO works badly will also work badly in MOSOL. In particular, the known lack of hydrogen bonding and excessive long-range repulsion in MNDO will also be reflected in MOSOL. NOTE:This system is distributed in VAX COPY format. FORTRAN 77 Lines of Code: 11839 |