Charge Fitting

class ChargeFitting

Charge fitting calculations can be carried out using the ChargeFitting() driver, which expects a QM-level Theory object, e.g.:

my_frag = Fragment(coords='my_frag.xyz')

my_theory = GAMESS_UK(frag=my_frag,
                      method='dft',
                      functional='b3lyp',
                      basis='6-31g*')

my_fit1 = ChargeFitting(theory=my_theory,
                        npoints=2400,
                        type='shell',
                        vdw_scale=1.5,
                        nlayers=2,
                        vdw_incr=0.2)

The charge fitting calculation is run with:

my_job.run(dryrun=False)

Then the resulting charges will be stored in my_frag.charges (see: <class Fragment>).

Methods

ChargeFitting.run()

Options

The single-point driver takes the following arguments:

theory

Choose the theory level by specifying a Theory instance

alpha

(default: 1.0) Search direction

a

(default: 0.0005) Constant a (in (Ha/e)**2)

b

(default: 0.2) Constant b (in elementary charge e)

conserve

(default: 10) Conserves the total charge every conserve cycles

constraints

(default: []) Constraint definition

frozen

(default: []) A list of indices of atoms to freeze

initial

(default: float('nan')) Initial values of charges

maxcycles

(default: 10000) Maximum cylces of iterations

maxinners

(default: 10) Maximum cycles of inner iterations

method

Allowed values: * 'resp': (default) Kolllman’s restrained electrostatic potential (RESP). See: C. I. Bayly, et al., J. Phys. Chem. 1993, 97, 10269

nlayers

(default: 4) Number of layers of grid points

npoints

(default: 200*theory.frag.natoms) Number of grid points to generate

tol_inner

(default: 1.0E-5) Tolerance of convergence for inner iterations

tolerance

(default: 1.0E-12) Tolerance of convergence

type

Allowed values: * 'shell': (default) Uses shell-like grid points

vdw_scale

(default: 1.2) van der Waals scale

vdw_incr

(default: 0.2) Increment of van der Waals : 0.4/nlayers**0.5