def get_potential_energy(self, atoms, force_consistent=False, dft_d_cutoff_radius=25.0):
"""
Altered version of the original get_potential_energy function
in the class Vasp. The function obtains the DFT energy by using
the original call for the VASP package and adds the DFT-D contribution
to the converged SCF-energy.
"""
# self.update(atoms)
#
# Get interaction list and matrix
interactionlist, interactionmatrix = get_interaction_controls(atoms)
#
# Calling original VASP-calculator for energy
self.energy_free_or_zero = vasp.Vasp.get_potential_energy(self, atoms, force_consistent)
#
# Call DFT-D module: Energy and gradients
self.dispersion_correction, self.dft_d_gradient_contribution = dftd.dft_d_pbc(atoms,
interactionlist=interactionlist,
interactionmatrix=interactionmatrix,
cutoff_radius=dft_d_cutoff_radius)
#
# Print out components (Useful?)
print
print 'DFT total energy : ', self.energy_free_or_zero
print 'DFT-D correction : ', self.dispersion_correction
print
print 'DFT-D final corrected energy: ', self.energy_free_or_zero + self.dispersion_correction
print
#
# Adding correction contribution to energy
return self.energy_free_or_zero + self.dispersion_correction
def get_forces(self, atoms, dft_d_cutoff_radius=25.0):
"""
Altered version of the original get_forces function in the Vasp-class.
The function obtains the DFT forces by using the original call for the
VASP package and adds the DFT-D contribution to the calculated forces.
"""
# self.update(atoms)
#
# Calling original VASP-calculator for forces
self.energy_free_or_zero = vasp.Vasp.get_forces(self, atoms)
#
# Get interaction list and matrix
interactionlist, interactionmatrix = get_interaction_controls(atoms)
#
# Call DFT-D module: Energy and gradients
self.dispersion_correction, self.dft_d_gradient_contribution = dftd.dft_d_pbc(atoms,
interactionlist=interactionlist,
interactionmatrix=interactionmatrix,
cutoff_radius=dft_d_cutoff_radius)
#
# Print out components (Useful?)
#print
#print 'DFT total forces : ', self.forces[0]
#for ind_i in range(1,len(self.forces)):
# print ' ', self.forces[ind_i]
#print 'DFT-D contribution : ', -self.dft_d_gradient_contribution[0]
#for ind_i in range(1,len(self.forces)):
# print ' ', -self.dft_d_gradient_contribution[ind_i]
#print
print
print 'DFT-D total gradients:', -self.dft_d_gradient_contribution[0] + self.forces[0]
for ind_i in range(1,len(self.forces)):
print ' ', -self.dft_d_gradient_contribution[ind_i] + self.forces[ind_i]
print
#
# Adding correction contributions to forces
# Note the (-) sign: DFT-D module delivers gradients, not forces
return self.forces - self.dft_d_gradient_contribution
