HO-MM-1 homonuclear molecular mechanics interface



Summary:

The HO-MM-1 interface is used for potential energy subprograms capable of handling an arbitrary number of identical atoms. The driver program passes the geometry as a set of cartesian coordinates for each atom, and the potential energy and first derivatives are returned.

Format and selected details:

In general, a HO-MM-1 potential energy routine has the following format:

SUBROUTINE POT( X, Y, Z, E, DEDX, DEDY, DEDZ, NATOM, MAXATOM)

DIMENSION X(MAXATOM), Y(MAXATOM), Z(MAXATOM)
DIMENSION DEDX(MAXATOM), DEDY(MAXATOM), DEDZ(MAXATOM)

E = SOME FUNCTION OF ( X, Y, and Z )
DEDX = SOME FUNCTION OF ( X, Y, and Z )
DEDY = SOME FUNCTION OF ( X, Y, and Z )
DEDZ = SOME FUNCTION OF ( X, Y, and Z )

RETURN

END

Required variables:

The subroutine POT takes the following arguments

POT ( X(NATOM), Y(NATOM), Z(NATOM), E, DEDX(NATOM), DEDY(NATOM), DEDZ(NATOM), NATOM, MAXATOM )
where

NATOM input, integer The number of identical atoms.

MAXATOM input, integer Sets the dimension of the cartesian variables X, Y, and Z. MAXATOM must be greater than or equal to NATOM.

X(NATOM)
Y(NATOM)
Z(NATOM)
input, double precision One-dimensional arrays containing the X, Y, and Z components of all NATOM atoms, where the index labels the atoms.

E output, double precision The potential energy.

DEDX(NATOM)
DEDY(NATOM)
DEDZ(NATOM)
output, double precision One-dimensional arrays containing the first derivatives of the energy E with respect to the X, Y, and Z components of all NATOM atoms, where the index labels the atoms.