Zopt

This is an implementation of probably the most important function in computational chemistry--molecular energy as a function of internal coordinates.

It must be passed a zmatrix definition and the type of computation to be used to generate the energy, gradients, and hessian, (with similar effects to the opt routine).

The implementation in ChemShell supports mixed z-matrix/Cartesian coordinates besides pure internal coordinates.

Argument	Argument type	Mandatory	Default	To specify
zmatrix=	Zmatrix tag	yes	none	geometry and optimisation variables
theory=	Energy/Gradient code	yes	none	what type of calculation to perform for energy and gradient
list_option=	keyword	no	full	amount of output required
punchfile=	File name	no	No punchfile generated	File to save sequence of structures generated, saved as cartesian coordinates
result=	Zmatrix tag	no	zopt.result	Where to save final structure

The following example uses the newopt function to perform a BFGS minimisation of the water molecule with a molecular mechanics energy expression.

#
z_create zmatrix=z {
zmatrix angstrom
o
h 1 oh
h 1 oh 2 hoh
variables 
oh  0.8
hoh 105.0
end
}

z_list zmatrix=z

read_input ff {
bond   o h   2000. 1.
angle h o h  300. 100.
}

newopt function=zopt: {theory=dl_poly : mm_defs=ff  zmatrix=z}