#!/usr/bin/env python
# Copyright 2014-2019 The PySCF Developers. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Authors: Chia-Nan Yeh <yehcanon@gmail.com>
#
'''
Generalized collinear Kohn-Sham in the spin-orbital basis for periodic systems with k-point sampling
See Also:
pyscf.pbc.dft.rks.py : General spin-orbital Kohn-Sham for periodic
systems at a single k-point
'''
import numpy as np
import scipy.linalg
from pyscf import lib
from pyscf.lib import logger
from pyscf.pbc.scf import khf
from pyscf.pbc.scf import kghf
from pyscf.pbc.dft import gen_grid
from pyscf.pbc.dft import krks
from pyscf.pbc.dft import rks
from pyscf.pbc.dft import multigrid
from pyscf.pbc.dft.numint2c import KNumInt2C
from pyscf import __config__
[docs]
def get_veff(ks, cell=None, dm=None, dm_last=0, vhf_last=0, hermi=1,
kpts=None, kpts_band=None):
'''Coulomb + XC functional for KGKS
Args:
ks : an instance of :class:`GKS`
XC functional are controlled by ks.xc attribute. Attribute
ks.grids might be initialized.
dm : ndarray or list of ndarrays
A density matrix or a list of density matrices
Returns:
Veff : (nkpts, 2*nao, 2*nao) or (*, nkpts, 2*nao, 2*nao) ndarray
Veff = J + Vxc.
'''
if cell is None: cell = ks.cell
if dm is None: dm = ks.make_rdm1()
if kpts is None: kpts = ks.kpts
t0 = (logger.process_clock(), logger.perf_counter())
ni = ks._numint
if ks.nlc or ni.libxc.is_nlc(ks.xc):
raise NotImplementedError(f'NLC functional {ks.xc} + {ks.nlc}')
hybrid = ni.libxc.is_hybrid_xc(ks.xc)
# TODO GKS with hybrid functional
hybrid = ks._numint.libxc.is_hybrid_xc(ks.xc)
if hybrid:
raise NotImplementedError
# TODO GKS with multigrid method
if isinstance(ks.with_df, multigrid.MultiGridFFTDF):
raise NotImplementedError
# ndim = 3 : dm.shape = (nkpts, nao, nao)
ground_state = (isinstance(dm, np.ndarray) and dm.ndim == 3 and
kpts_band is None)
ks.initialize_grids(cell, dm, kpts, ground_state)
# TODO: support non-symmetric density matrix
assert (hermi == 1)
max_memory = ks.max_memory - lib.current_memory()[0]
ni = ks._numint
n, exc, vxc = ni.get_vxc(cell, ks.grids, ks.xc, dm, hermi=hermi, kpts=kpts,
kpts_band=kpts_band, max_memory=max_memory)
logger.debug(ks, 'nelec by numeric integration = %s', n)
t0 = logger.timer(ks, 'vxc', *t0)
nkpts = len(kpts)
weight = 1. / nkpts
if not hybrid:
vj = ks.get_j(cell, dm, hermi, kpts, kpts_band)
vxc += vj
else:
omega, alpha, hyb = ks._numint.rsh_and_hybrid_coeff(ks.xc, spin=cell.spin)
vj, vk = ks.get_jk(cell, dm, hermi, kpts, kpts_band)
vk *= hyb
if omega != 0:
vklr = ks.get_k(cell, dm, hermi, kpts, kpts_band, omega=omega)
vklr *= (alpha - hyb)
vk += vklr
vxc += vj - vk
if ground_state:
exc -= np.einsum('Kij,Kji', dm, vk).real * .5
if ground_state:
ecoul = np.einsum('Kij,Kji', dm, vj).real * .5 * weight
else:
ecoul = None
vxc = lib.tag_array(vxc, ecoul=ecoul, exc=exc, vj=None, vk=None)
return vxc
[docs]
class KGKS(rks.KohnShamDFT, kghf.KGHF):
'''GKS class adapted for PBCs with k-point sampling.
'''
get_veff = get_veff
energy_elec = krks.energy_elec
get_rho = krks.get_rho
def __init__(self, cell, kpts=np.zeros((1,3)), xc='LDA,VWN',
exxdiv=getattr(__config__, 'pbc_scf_SCF_exxdiv', 'ewald')):
kghf.KGHF.__init__(self, cell, kpts, exxdiv=exxdiv)
rks.KohnShamDFT.__init__(self, xc)
self._numint = KNumInt2C()
[docs]
def dump_flags(self, verbose=None):
kghf.KGHF.dump_flags(self, verbose)
rks.KohnShamDFT.dump_flags(self, verbose)
return self
[docs]
def x2c1e(self):
'''Adds spin-orbit coupling effects to H0 through the x2c1e approximation'''
from pyscf.pbc.x2c.x2c1e import x2c1e_gscf
return x2c1e_gscf(self)
x2c = x2c1e
[docs]
def stability(self):
raise NotImplementedError
[docs]
def nuc_grad_method(self):
raise NotImplementedError
[docs]
def to_hf(self):
'''Convert to KGHF object.'''
from pyscf.pbc import scf
return self._transfer_attrs_(scf.KGHF(self.cell, self.kpts))