The program minimises interaction energy between a rare-gas atom and a molecule, which is assumed to consist of dispersive attraction counterbalanced by hard sphere repulsion. The anisotropy of the dispersive interaction is modeled by replacing atomic polarisabilities by cubes of their covalent radii.

        References: 

• Z.Kisiel, J.Phys.Chem. 95, 7605-7612 (1991) - model
• Z.Kisiel, P.W.Fowler, A.C.Legon, J.Chem.Phys. 95, 2283-2291 (1991) - use of model to rationalise geometries of Ar...CH₂CHF, Ar...CH₂CF₂, Ar...CHFCF₂

        Principal features:

• automatic assignment of model parameters which can be overridden
• fixed geometry calculation
• full and limited minimisation (eg. for potential characterisation)
• Rg-atom translation vector can be either Cartesian or polar
• input of translation vector from keyboard or file
• output to screen and two types of files

        RGDMIN runs interactively and can use up to four different files:

• Main input file with containing molecular data, specified at run-time by the user
• Optional file containing initial starting positions of Rare gas atom B, user named
• Main output file containing results of minimisations, user named
• Ancillary output file containing details of individual iterations, this has a fixed name: MONITOR

        RGDMIN is a much simplified derivative version of MIN16.

	RGDMIN.FOR The listing. RGDMIN.EXE Executable for any PC, from compilation with MSF5. Runs from the command line.   Examples OFTKR.RGD Data file for o-F-toluene...Kr OFTKR.RES Results file containing the principal geometries identified using starting positions in STARTG.RGD. STARTRG.CFG An array of starting coordinates for minimisation of dimer geometry. The idea is to provide either a hemisphere or a sphere of starting points so that the most important local minima will be located. MONITOR The MONITOR file summarising the geometries for the complex above located with STARTRG.CFG. Note that, in general, quite a few local minima will be found. The majority are physically sensible, but some may be an artifact of the hard sphere repulsion used in the model - see Fig.8 of the paper on the model. In the present case RUN.1 converges to the global minimum, RUN.4 is probably a spurious minimum very close to the global one, RUN.23 is a competing local minimum, RUN.29 is an insignificant local minimum.

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        This program is descended directly from Patrick Fowler's program V used in the development of the electrostatic model.

        The B&F model is based on the idea that the dominant contribution to interaction energy comes from the electrostatic term. This can be rather satisfactorily modeled by using the distributed multipole analysis (DMA) of electron charge distribution, and the resulting attractive electrostatic term is counterbalanced by a hard van der Waals sphere repulsive term. The program searches for minima in intermolecular interaction energy between molecules A and B by reorienting molecule B around molecule A.

        Note that a rather more developed program for such calculations, ORIENT, is available from Anthony Stone in Cambridge.

        References:

• Buckingham and Fowler, J.Chem.Phys. 79, 6426 (1983) - electrostatic model
• Buckingham and Fowler, Can.J.Chem. 63, 2018 (1985) - electrostatic model
• Price and Stone, J.Chem.Phys. 86, 2859 (1987) - repulsive wall as used in MIN16
• Stone, Chem.Phys.Lett. 83, 233 (1981) - DMA
• Kisiel, Fowler, Legon, J. Chem. Phys. 93, 3054 (1990); 93, 6249 (1990); 101, 4635 (1994) - some of the first applications of this program
• A.D.Buckingham - in Intermolecular Interactions - From Diatomics to Biopolymers: Pullman, B., Ed.; Wiley: New York, 1978; Chapter 1 - invaluable tutorial on concepts and procedures used in MIN16

       Key features of MIN16:

• calculation of electrostatic interaction energy (E_es)_int up to quadrupole
• calc of (E_es)_int with all terms up to t₄ = t_abgd (ie all quadrupole terms and charge.octopole + dipole.octopole + charge-hexadecapole)
• calc of (E_es)_int with all terms up to octopole (t₆)
• calc of (E_es)_int limited by t₆ and hexadecapole
• calc of (E_es)_int limited by t₇ and hexadecapole
• calc of (E_es)_int with all terms up to hexadecapole (t₈)
• full minimisation (6 parameters = 3 in translation vector, and 3 rotation angles of molecule B relative to A)
• limited minimisation - only one of the three translation vector parameters (R) is minimised
• fixed geometry calculation
• translation vector input in either Cartesian or polar form
• input of translation vector from keyboard or file
• output to screen and two types of files
• recovery of molecular multipoles from distributed multipoles
• inspection of selected structural parameters

       MIN16 is accompanied by several programs for extracting DMA's from output of various ab initio packages and for managing DMA arrays.

	MIN16.FOR The listing - this is a straightforward numbercrunching program and has been compiled on several hardware/software architectures including Pentium/SG/DOS/UNIX. The use of the -static option for the f77 compiler family is mandatory. MIN16.EXE Executable for Win98/Win2K/XP.   Examples MECPHF.HEX Sample data file, for the methylenecyclopropane...HF hydrogen bonded dimer. This was used to produce the results reported in Chem.Phys.Lett. 232, 187 (1995). MECPHF.RES Abbreviated results file for the above, with runs identifying the two geometries reported in the paper. Each section containing the Cartesians for the minimised geometry can be cut out and viewed directly with PMIFST. MECPHF.MON The monitor file showing abbreviated results of minimisations carried out from starting points in START.CFG. Note how these results split between the two geometries. START.CFG File containing an array of starting configurations for the minimisation. The idea is to provide either a hemisphere or a sphere of starting points so that the most important local minima will be located.   Companion programs EXTRACT.FOR Extraction of DMA from output of CADMAC, SYSMO (and possibly GAMESS UK) and conversion into the form used by MIN16. Not used for some time and might need some modification. GAMDMA.FOR Extraction of DMA from GAMESS output and conversion into the form for MIN16. This has almost exclusively been used with PC GAMESS - note that GAMESS only produces DMA's up to octopole and the hexadecapoles are set to zero. DMAROT.FOR Program for transformations (rotation, translation, shift of expansion origin) on a DMA array.

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