$EFRAG

$EFRAG group (optional)

This group gives the name and position of one or more effective fragment potentials. It consists of a series of free format card images, which may not be combined onto a single line! The position of a fragment is defined by giving any three points within the fragment, relative to the ab initio system defined in $DATA, since the effective fragments have a frozen internal geometry. All other atoms within the fragment are defined by information in the $FRAGNAME group.


-1- a line containing one or more of these options:

COORD
=CART selects use of Cartesians coords to define the fragment position at line -3-. (default)

=INT selects use of Z-matrix internal coordinates at line -3-.

POLMETHD
=SCF indicates the induced dipole for each fragment due to the ab initio electric field and other fragment fields is updated only once during each SCF iteration.

=FRGSCF requests microiterations during each SCF iteration to make induced dipoles due to ab initio and other fragment fields self consistent amoung the fragments. (default) Both methods converge to the same dipolar interaction.

POSITION
=OPTIMIZE Allows full optimization within the ab initio part, and optimization of the rotational and translational motions of each fragment. (default)

=FIXED Allows full optimization of the ab initio system, but freezes the position of the fragments. This makes sense only with two or more fragments, as what is frozen is the fragments' relative orientation.

=EFOPT the same as OPTIMIZE, but if the fragment gradient is large, up to 5 geometry steps in which only the fragments move may occur, before the geometry of the ab initio piece is relaxed. This may save time by reusing the two electron integrals for the ab initio system.

Input a blank line if all the defaults are acceptable.


-2- FRAGNAME=XXX,

XXX is the name of the fragment whose coordinates are to be given next. All other information defining the fragment is given in a supplemental $XXX group, which is referred to below as a $FRAGNAME group.

A RHF/DZP EFP for water is internally stored in GAMESS. Choose FRAGNAME=H2OEF2 to look up this numerical data, and then skip the input of $H2OEF2 and $FRGRPL groups.


-3- NAME, X, Y, Z (COORD=CART)
NAME, I, DISTANCE, J, BEND, K, TORSION (COORD=INT)

NAME
= the name of a fragment point. The name used here must match one of the points in $FRAGNAME.

X, Y, Z
= Cartesian coordinates defining the position of this fragment point RELATIVE TO THE COORDINATE ORIGIN used in $DATA. The choice of units is controlled by UNITS in $CONTRL.

I, DISTANCE, J, BEND, K, TORSION
= the usual Z-matrix connectivity internal coordinate definition. The atoms I, J, K must be atoms in the ab initio system from in $DATA, or fragment points already defined in the current fragment or previously defined fragments.

Line -3- must be given a total of three times to define this fragment's position.


Repeat lines -2- and -3- to enter as many fragments as you desire, and then end the group with a $END line.

Note that it is quite typical to repeat the same fragment name at line -2-, to use the same fragment system at many different positions.


For tips on effective fragment potentials see the 'further information' section


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