Ligands.FitCharges

Ligands.FitCharges(self, chisqfunc, fitargs, method='Powell', **kwargs):

Fit the effective charges of a point charge model by minimizing a user-provided chi squared function chisqfunc.

Parameters

• chisqfunc: function, defining the chi^2 to be minimized. The first input argument must be a Ligands object, the rest are inputs that may or may not be minimized. Example:

def GlobalError(LigandsObject, LigandCharge, EnergyOffset):
    # Build Hamiltonian
    newH = LigandsObject.PointChargeModel(symequiv, LigandCharge=LigandCharge, printB=False)
    newH.diagonalize()

    # Compute error in eigenvalues
    return sum((newH.eigenvalues.real + EnergyOffset - ObservedEigenvals)**2)

• fitargs: list of strings, giving the names of the variables to be fitted. For example, if chisqfunc = GlobalError above, one could set fitargs = ['LigandCharge','EnergyOffset'] or fitargs = ['LigandCharge'], or fitargs = ['EnergyOffset'].
• method: string, minimization method from the scipy library. Default: 'Powell'
• kwargs: dictionary, other arguments to be passed to the scipy.optimize.minimize function.

Returns

• newH: a CFLevels object giving the CEF Hamiltonian from the final fitted point charge model.
• finalvals: a dictionary with the fitted values of the fitargs.