#!/usr/bin/env python
# Copyright 2014-2021 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.
#
# Author: Timothy Berkelbach <tim.berkelbach@gmail.com>
#
'''
Restricted QCISD implementation
The 4-index integrals are saved on disk entirely (without using any symmetry).
Note MO integrals are treated in chemist's notation
Ref:
'''
import numpy
import numpy as np
from pyscf import lib
from pyscf.lib import logger
from pyscf.cc import rccsd_slow as rccsd
from pyscf.cc import rintermediates as imd
from pyscf import __config__
BLKMIN = getattr(__config__, 'cc_ccsd_blkmin', 4)
MEMORYMIN = getattr(__config__, 'cc_ccsd_memorymin', 2000)
[docs]
def kernel(mycc, eris=None, t1=None, t2=None, max_cycle=50, tol=1e-8,
tolnormt=1e-6, verbose=None):
'''Same as ccsd.kernel with strings modified to correct the method name'''
log = logger.new_logger(mycc, verbose)
if eris is None:
eris = mycc.ao2mo(mycc.mo_coeff)
if t1 is None and t2 is None:
t1, t2 = mycc.get_init_guess(eris)
elif t2 is None:
t2 = mycc.get_init_guess(eris)[1]
cput1 = cput0 = (logger.process_clock(), logger.perf_counter())
eold = 0
eccsd = mycc.energy(t1, t2, eris)
log.info('Init E_corr(QCISD) = %.15g', eccsd)
if isinstance(mycc.diis, lib.diis.DIIS):
adiis = mycc.diis
elif mycc.diis:
adiis = lib.diis.DIIS(mycc, mycc.diis_file, incore=mycc.incore_complete)
adiis.space = mycc.diis_space
else:
adiis = None
conv = False
for istep in range(max_cycle):
t1new, t2new = mycc.update_amps(t1, t2, eris)
tmpvec = mycc.amplitudes_to_vector(t1new, t2new)
tmpvec -= mycc.amplitudes_to_vector(t1, t2)
normt = numpy.linalg.norm(tmpvec)
tmpvec = None
if mycc.iterative_damping < 1.0:
alpha = mycc.iterative_damping
t1new = (1-alpha) * t1 + alpha * t1new
t2new *= alpha
t2new += (1-alpha) * t2
t1, t2 = t1new, t2new
t1new = t2new = None
t1, t2 = mycc.run_diis(t1, t2, istep, normt, eccsd-eold, adiis)
eold, eccsd = eccsd, mycc.energy(t1, t2, eris)
log.info('cycle = %d E_corr(QCISD) = %.15g dE = %.9g norm(t1,t2) = %.6g',
istep+1, eccsd, eccsd - eold, normt)
cput1 = log.timer('QCISD iter', *cput1)
if abs(eccsd-eold) < tol and normt < tolnormt:
conv = True
break
log.timer('QCISD', *cput0)
return conv, eccsd, t1, t2
[docs]
def update_amps(cc, t1, t2, eris):
# Ref: Hirata et al., J. Chem. Phys. 120, 2581 (2004) Eqs.(35)-(36)
nocc, nvir = t1.shape
fock = eris.fock
fov = fock[:nocc,nocc:].copy()
foo = fock[:nocc,:nocc].copy()
fvv = fock[nocc:,nocc:].copy()
Foo = imd.cc_Foo(0*t1,t2,eris)
Fvv = imd.cc_Fvv(0*t1,t2,eris)
Fov = imd.cc_Fov(t1,t2,eris)
Foo -= np.diag(np.diag(foo))
Fvv -= np.diag(np.diag(fvv))
# T1 equation
t1new = np.asarray(fov).conj().copy()
t1new += lib.einsum('ac,ic->ia', Fvv, t1)
t1new += -lib.einsum('ki,ka->ia', Foo, t1)
t1new += 2*lib.einsum('kc,kica->ia', Fov, t2)
t1new += -lib.einsum('kc,ikca->ia', Fov, t2)
t1new += 2*lib.einsum('kcai,kc->ia', eris.ovvo, t1)
t1new += -lib.einsum('kiac,kc->ia', eris.oovv, t1)
eris_ovvv = np.asarray(eris.ovvv)
t1new += 2*lib.einsum('kdac,ikcd->ia', eris_ovvv, t2)
t1new += -lib.einsum('kcad,ikcd->ia', eris_ovvv, t2)
t1new +=-2*lib.einsum('kilc,klac->ia', eris.ooov, t2)
t1new += lib.einsum('likc,klac->ia', eris.ooov, t2)
# T2 equation
t2new = np.asarray(eris.ovov).conj().transpose(0,2,1,3).copy()
Loo = imd.Loo(0*t1, t2, eris)
Lvv = imd.Lvv(0*t1, t2, eris)
Loo -= np.diag(np.diag(foo))
Lvv -= np.diag(np.diag(fvv))
Woooo = imd.cc_Woooo(0*t1, t2, eris)
Wvoov = imd.cc_Wvoov(0*t1, t2, eris)
Wvovo = imd.cc_Wvovo(0*t1, t2, eris)
Wvvvv = imd.cc_Wvvvv(0*t1, t2, eris)
t2new += lib.einsum('klij,klab->ijab', Woooo, t2)
t2new += lib.einsum('abcd,ijcd->ijab', Wvvvv, t2)
tmp = lib.einsum('ac,ijcb->ijab', Lvv, t2)
t2new += (tmp + tmp.transpose(1,0,3,2))
tmp = lib.einsum('ki,kjab->ijab', Loo, t2)
t2new -= (tmp + tmp.transpose(1,0,3,2))
tmp = 2*lib.einsum('akic,kjcb->ijab', Wvoov, t2)
tmp -= lib.einsum('akci,kjcb->ijab', Wvovo, t2)
t2new += (tmp + tmp.transpose(1,0,3,2))
tmp = lib.einsum('akic,kjbc->ijab', Wvoov, t2)
t2new -= (tmp + tmp.transpose(1,0,3,2))
tmp = lib.einsum('bkci,kjac->ijab', Wvovo, t2)
t2new -= (tmp + tmp.transpose(1,0,3,2))
tmp2 = np.asarray(eris.ovvv).conj().transpose(1,3,0,2)
tmp = lib.einsum('abic,jc->ijab', tmp2, t1)
t2new += (tmp + tmp.transpose(1,0,3,2))
tmp2 = np.asarray(eris.ooov).transpose(3,1,2,0).conj()
tmp = lib.einsum('akij,kb->ijab', tmp2, t1)
t2new -= (tmp + tmp.transpose(1,0,3,2))
mo_e = eris.fock.diagonal().real
eia = mo_e[:nocc,None] - mo_e[None,nocc:]
eijab = lib.direct_sum('ia,jb->ijab',eia,eia)
t1new /= eia
t2new /= eijab
return t1new, t2new
[docs]
class QCISD(rccsd.RCCSD):
'''restricted QCISD
'''
[docs]
def kernel(self, t1=None, t2=None, eris=None):
return self.qcisd(t1, t2, eris)
[docs]
def qcisd(self, t1=None, t2=None, eris=None):
assert (self.mo_coeff is not None)
assert (self.mo_occ is not None)
if self.verbose >= logger.WARN:
self.check_sanity()
self.dump_flags()
self.e_hf = self.get_e_hf()
if eris is None:
eris = self.ao2mo(self.mo_coeff)
self.converged, self.e_corr, self.t1, self.t2 = \
kernel(self, eris, t1, t2, max_cycle=self.max_cycle,
tol=self.conv_tol, tolnormt=self.conv_tol_normt,
verbose=self.verbose)
self._finalize()
return self.e_corr, self.t1, self.t2
[docs]
def energy(self, t1=None, t2=None, eris=None):
return rccsd.energy(self, t1*0, t2, eris)
update_amps = update_amps
[docs]
def qcisd_t(self, t1=None, t2=None, eris=None):
from pyscf.cc import qcisd_t_slow as qcisd_t
if t1 is None: t1 = self.t1
if t2 is None: t2 = self.t2
if eris is None: eris = self.ao2mo(self.mo_coeff)
return qcisd_t.kernel(self, eris, t1, t2, self.verbose)
[docs]
def density_fit(self, auxbasis=None, with_df=None):
raise NotImplementedError
if __name__ == '__main__':
from pyscf import gto, scf
mol = gto.Mole()
mol.atom = """C 0.000 0.000 0.000
H 0.637 0.637 0.637
H -0.637 -0.637 0.637
H -0.637 0.637 -0.637
H 0.637 -0.637 -0.637"""
mol.basis = 'cc-pvdz'
mol.verbose = 7
mol.spin = 0
mol.build()
mf = scf.RHF(mol).run(conv_tol=1e-14)
mycc = QCISD(mf, frozen=1)
ecc, t1, t2 = mycc.kernel()
print(mycc.e_tot - -40.383989)
et = mycc.qcisd_t()
print(mycc.e_tot+et - -40.387679)
