AIMPAC Utilities schuss(3) NAME schuss - calculates gradient paths in a charge distribution SYNOPSIS schuss vecfile wfnfile DESCRIPTION schuss calculates gradient paths in a charge distribution in a plane requested by the user, outputting the calculated paths into a file (gvp) ready to be sent to the plotter. The vecfile contains the number and type of starting points of gradient paths desired, as outlined below. The wfnfile contains the wave-function for the system in terms of primitive basis functions calculated by one of the ab-initio molecular orbital packages. ARGUMENTS vecfile (for example 'c4h4.vec') The vecfile, described below, describes the orientation of the chosen plane, the number, and the types of origins desired within that plane. wfnfile (for example 'c4h4.wfn') The wavefunction file contains the basis set and optimized coefficients from a SCF calculation describing the charge distribution of that molecule. FORMAT The input to SCHUSS is free format with the first seven characters of each card being ignored by the routine and used by the user as labels for ease of use. An example of the input is given here. TITLE: Tetrahedrane HF/6-31G**/HF/6-31G* PLOT: 10.0 0.100 CENTR: 0.0 0.0 0.0 PARAM: 0.1 0.005 0.005 1.0E-12 0 1 PLANE: 0 1 2 5 6 NORIG: 4 0.97775600 -0.97775600 -0.97775600 0 0 36 -0.97775600 -0.97775600 0.97775600 0 0 36 6.36117174E-09 -1.15576876E+00 1.59025028E-08 1 2 2 1.72948502E+00 -1.72948502E+00 -1.72948502E+00 1 2 2 The cards are used as follows: TITLE: Tetrahedrane HF/6-31G**/HF/6-31G* The first card is a 60 character title card. PLOT: 10.0 0.100 The second card defines the grid size and density. The first real number (N1) is the length of either axis of the grid in atomic units (all values are in atomic units). The second real number (N2) is the distance between each grid point along the axis. This defines the density of the grid as there will be N1/N2 points along each axis and hence (N1/N2)**2 grid points in total. SCHUSS uses this information for scaling of the plots only, not in the determination of the gradient paths. It is a good and suggested practice to use the same values for PLOT for SCHUSS as used in GRID. CENTR: 0.0 0.0 0.0 The third card defines the center of the plot in the molecular frame of reference. The grid will be evenly placed about this point. PARAM: 0.1 0.005 0.005 1.0E-12 0 1 The PARAM line contains five parameters used in the walking algorithm. The first number is the distance (in a.u., as are the rest) from an attractor that the walk is started. The second and third are the distances from the defined repellors that the uphill and downhill walks are started, respectively. The fourth number is the endpoint criterion for all walks. The next number determines whether the gradient vector paths are allowed out of the plane or not. A zero (0) means that the paths are to remain in the plane and a one (1) allows the gradient vectors to leave the plane of the atoms. The former is used most often while the latter is used primarily for molecular graphs. The last number is the slow/fast walking switch. A zero (0) means walk slowly (carefully) and a one (1) means step quickly. The fast switch should be set first and only turned off if difficulty is encountered. PLANE: 0 1 2 5 6 The fourth card allows the user to define the plane of interest for this calculation rotating it to the XY plane of the plotter. The user has a choice of two methods for description of the plane, inertial axis or Euler angles. The first integer read determines which method is used. If the integer value is zero inertial axis is to be used. The integers following are the atom numbers of those atoms within the plane. Any number of atoms (up to 30) may be used to define the plane (three atoms define a plane, but more may be entered). In this case, the user has requested that atoms 1, 2, 5, and 6 be placed in the plane. If the atoms do not define a plane, the routine will make a best fit to the plane and the results will most likely not be desirable. Dummy atoms may be used to define the plane as well. In this case use negative integers to specify each dummy atom. The dummy atom coordinates must be entered on the card(s) right after the PLANE card. If the integer value is 1 then Euler angles will be used. The first real number is the rotation, in degrees, about the molecular Z axis. (Positive rotations correspond to clockwise rotations when viewing down that axis toward the origin from the positive axis) The second real number is the rotation about the molecular X axis. The third is the rotation about the Z axis of the plotter's frame. For example if the tetrahedrane molecule were such that the four atoms of interest were in the YZ plane in the wavefunction file the following card would place those atoms in the plotter's XY plane. PLANE: 1 90.0 90.0 0.0 This corresponds to rotation about the Z axis, placing the atoms in the XZ plane. The second rotation about the X axis places the atoms in the XY plane. And the user has decided not to reorient the plane now that it is in the XY plane, hence the third angle is 0.0. NORIG: 4 This card inputs the number of origins to be used. SCHUSS is dimensioned to handle up to 60 origins. Following this card are NORIG cards upon which are the origin coordinates and descriptors. 0.97775600 -0.97775600 -0.97775600 0 0 36 -0.97775600 -0.97775600 0.97775600 0 0 36 6.36117174E-09 -1.15576876E+00 1.59025028E-08 1 2 2 1.72948502E+00 -1.72948502E+00 -1.72948502E+00 1 2 2 Each card lists the Cartesian coordinates of the origin followed be three integers describing the type of origin and number of ascending and descending gradient paths from that origin. A (2,- 2) origin in the plane is an attractor in that plane and is described by a descriptor '0'. From each attractor there are no ascending paths of grad rho, only descending. (i.e. from that point of grad rho may only decrease in the plane. For the first two cards in the example, each is an attractor in the chosen plane and the user has requested that 36 descending gradient paths be mapped from each one. The other critical point of interest in a plane is the (2,0) (the (2,+2) paths are always the end points of gradient paths and will always be found by descending paths in grad rho from the other two types of critical points.) and it is described by a descriptor of '1'. The user has requested that 2 ascending and 2 descending gradient paths be calculated from these points. OUTPUT SCHUSS generates an output file with the file extension '.gvp' which contains the calculated gradient paths. This file may be plotted by redirecting the output to the plotter. On unix machines, the appropriate command would be: $ cat c4h4.gvp > /dev/tty02 (printer device) EXAMPLES schuss c4h4 c4h4 This requests the calculation of the gradient vector paths from the origins as described in the file c4h4.vec using the wavefunction in c4h4.wfn. INSTALLATION Compile with full vectorization optimization. Make sure you are using the appropriate Matrix multiplication routines in the GAUS subroutines. SEE ALSO extreme(3), grid(3), contor(3), relief(3), cube(3), envelope(3) Release 1.0 AIMPAC schuss(3)