$SURF

$SURF group (relevant for RUNTYP=SURFACE)

This group allows you to probe a potential energy surface along a small grid of points.
Note that there is no option to vary angles, only distances. The scan can be made for any SCFTYP, or for the MP2 or CI surface. You may specify two rather different calculations to be done at each point on the grid, through the RUNTYPn, SCFTYPn, and electron correlation keywords.

* * * below, 1 and 2 refer to different calculations * * *

RUNTP1,RUNTYP2 = some RUNTYP supported in $CONTRL
First RUNTYP=RUNTP1 and then RUNTYP=RUNTP2 will be performed, for each point on the grid. The second run is omitted if RUNTP2 is set to NONE.
default: RUNTP1=ENERGY  RUNTP2=NONE
SCFTP1,SCFTP2 = some SCFTYP supported in $CONTRL
default: SCFTYP in $CONTRL
CITYP1,CITYP2 = some CITYP supported in $CONTRL
default: CITYP in $CONTRL
MPLEV1,MPLEV2 = some MPLEVL supported in $CONTRL
default: MPLEVL in $CONTRL
CCTYP1,CCTYP2 = some CCTYP supported in $CONTRL
default: CCTYP in $CONTRL
DFTYP1,DFTYP2 = some DFTTYP supported in $DFT
default: DFTTYP in $DFT
You may need to help by giving values in $CONTRL that will permit the program to estimate what is coming in the values here. For example, if you want to request hessians here, it may be good to give RUNTYP=HESSIAN in $CONTRL so that in its earliest stages of a job, the program can initialize for 2nd derivatives. There is less checking here than on $CONTRL input, so don't request something impossible such as two correlaton methods simultaneously, or analytic hessians for MP2, or other things that are impossible.

* * * below, 1 and 2 refer to different coordinates * * *

IVEC1 = an array of two atoms, defining a coordinate from the first atom given to the second.
IGRP1 = an array specifying a group of atoms, which must include the second atom given in IVEC1. The entire group will be translated (rigidly) along the vector IVEC1, relative to the first atom given in IVEC1.
ORIG1 = starting value of the coordinate, which may be positive or negative. Zero corresponds to the distance given in $DATA.
DISP1 = step size for the coordinate. If DISP1 is set to zero, then the keyword $SURF GRID1 is read.
NDISP1 = number of steps to take for this coordinate.
GRID1 = an array of grid points at which to compute the energy. This option is an alternative to the ORIG1, DISP1 input which produces an equidistant grid. To use GRID1, one has to set DISP1=0.0. The number of grid points is in
NDISP1, and is limite to at most 100 grid points. The input of GRID1(1)=ORIG1,ORIG1+DISP1,ORIG1+DISP1*2,... would reproduce an equidistant grid given by ORIG1 and DISP1.
ORIG1, DISP1, and GRID1 should be given in Angstrom. There are no reasonable defaults for these keywords.
IVEC2, IGRP2, ORIG2, DISP2, NDISP2, GRID2 have the same meaning as their "1" counterparts, and permit you to make counterparts, and permit you to make a two dimensional map along two displacement coordinates. If the "2" data are not input, the surface map proceeds in only one dimension.