#!/usr/bin/env python
# Copyright 2014-2020 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: Xing Zhang <zhangxing.nju@gmail.com>
#
import time
import numpy as np
from scipy.linalg import block_diag
from pyscf import __config__
from pyscf import lib
from pyscf.lib import logger, einsum
from pyscf.lib.parameters import LARGE_DENOM
from pyscf.pbc.mp import kmp2
WITH_T2 = getattr(__config__, 'mp_mp2_with_t2', False)
[docs]
def kernel(mp, mo_energy, mo_coeff, verbose=logger.NOTE, with_t2=WITH_T2):
if with_t2:
return kernel_with_t2(mp, mo_energy, mo_coeff, verbose, with_t2)
else:
t2 = None
t0 = (logger.process_clock(), logger.perf_counter())
nmo = mp.nmo
nocc = mp.nocc
nvir = nmo - nocc
nkpts = mp.nkpts
kd = mp.kpts
eia = np.zeros((nocc,nvir))
eijab = np.zeros((nocc,nocc,nvir,nvir))
fao2mo = mp._scf.with_df.ao2mo
oovv_ij = np.zeros((nkpts,nocc,nocc,nvir,nvir), dtype=mo_coeff[0].dtype)
mo_e_o = [mo_energy[k][:nocc] for k in range(nkpts)]
mo_e_v = [mo_energy[k][nocc:] for k in range(nkpts)]
# Get location of non-zero/padded elements in occupied and virtual space
nonzero_opadding, nonzero_vpadding = kmp2.padding_k_idx(mp, kind="split")
kijab, weight, k4_bz2ibz = kd.make_k4_ibz(sym='s2')
_, igroup = np.unique(kijab[:,:2], axis=0, return_index=True)
igroup = igroup.ravel()
igroup = list(igroup) + [len(kijab)]
emp2_ss = emp2_os = 0.
nao2mo = 0
icount = 0
for i in range(len(igroup)-1):
istart = igroup[i]
iend = igroup[i+1]
kab = []
for j in range(istart, iend):
a, b = kijab[j][2:]
kab.append([a, b])
kab.append([b, a])
kab = np.unique(np.asarray(kab), axis=0)
ki = kijab[istart][0]
kj = kijab[istart][1]
kpts_i = kd.kpts[ki]
kpts_j = kd.kpts[kj]
orbo_i = mo_coeff[ki][:,:nocc]
orbo_j = mo_coeff[kj][:,:nocc]
for (ka, kb) in kab:
kpts_a = kd.kpts[ka]
kpts_b = kd.kpts[kb]
orbv_a = mo_coeff[ka][:,nocc:]
orbv_b = mo_coeff[kb][:,nocc:]
oovv_ij[ka] = fao2mo((orbo_i,orbv_a,orbo_j,orbv_b),
(kpts_i,kpts_a,kpts_j,kpts_b),
compact=False).reshape(nocc,nvir,nocc,nvir).transpose(0,2,1,3) / nkpts
nao2mo += 1
for j in range(istart, iend):
ka = kijab[j][2]
kb = kijab[j][3]
# Remove zero/padded elements from denominator
eia = LARGE_DENOM * np.ones((nocc, nvir), dtype=mo_energy[0].dtype)
n0_ovp_ia = np.ix_(nonzero_opadding[ki], nonzero_vpadding[ka])
eia[n0_ovp_ia] = (mo_e_o[ki][:,None] - mo_e_v[ka])[n0_ovp_ia]
ejb = LARGE_DENOM * np.ones((nocc, nvir), dtype=mo_energy[0].dtype)
n0_ovp_jb = np.ix_(nonzero_opadding[kj], nonzero_vpadding[kb])
ejb[n0_ovp_jb] = (mo_e_o[kj][:,None] - mo_e_v[kb])[n0_ovp_jb]
eijab = lib.direct_sum('ia,jb->ijab',eia,ejb)
t2_ijab = np.conj(oovv_ij[ka]/eijab)
idx_ibz = k4_bz2ibz[ki*nkpts**2 + kj*nkpts + ka]
assert(icount == idx_ibz)
edi = einsum('ijab,ijab', t2_ijab, oovv_ij[ka]).real * 2
exi = -einsum('ijab,ijba', t2_ijab, oovv_ij[kb]).real
emp2_ss += (edi*0.5 + exi) * weight[idx_ibz] * nkpts**3
emp2_os += edi*0.5 * weight[idx_ibz] * nkpts**3
icount += 1
emp2_ss /= nkpts
emp2_os /= nkpts
emp2 = lib.tag_array(emp2_ss+emp2_os, e_corr_ss=emp2_ss, e_corr_os=emp2_os)
assert(icount == len(kijab))
logger.debug(mp, "Number of ao2mo transformations performed in KMP2: %d", nao2mo)
logger.timer(mp, 'KMP2', *t0)
return emp2, t2
[docs]
def kernel_with_t2(mp, mo_energy, mo_coeff, verbose=logger.NOTE, with_t2=WITH_T2):
#we need almost all t2 for computing rdm, so simply use kmp2 without symmetry
kd = mp.kpts
mp.kpts = kd.kpts
emp2, t2 = kmp2.kernel(mp, mo_energy, mo_coeff, verbose, with_t2)
mp.kpts = kd
return emp2, t2
[docs]
@lib.with_doc(kmp2.make_rdm1.__doc__)
def make_rdm1(mp, t2=None, kind="compact"):
if kind not in ("compact", "padded"):
raise ValueError("The 'kind' argument should be either 'compact' or 'padded'")
d_imds = _gamma1_intermediates(mp, t2=t2)
result = []
padding_idxs = kmp2.padding_k_idx(mp, kind="joint")
for (oo, vv), idxs in zip(zip(*d_imds), padding_idxs):
oo += np.eye(*oo.shape)
d = block_diag(oo, vv)
d += d.conj().T
if kind == "padded":
result.append(d)
else:
result.append(d[np.ix_(idxs, idxs)])
return result
[docs]
def make_t2_for_rdm1(mp):
nmo = mp.nmo
nocc = mp.nocc
nvir = nmo - nocc
nkpts = mp.nkpts
kd = mp.kpts
kpts = kd.kpts
k_ibz = kd.ibz2bz
mo_coeff, mo_energy = kmp2._add_padding(mp, mp.mo_coeff, mp.mo_energy)
eia = np.zeros((nocc,nvir))
eijab = np.zeros((nocc,nocc,nvir,nvir))
fao2mo = mp._scf.with_df.ao2mo
mo_e_o = [mo_energy[k][:nocc] for k in range(nkpts)]
mo_e_v = [mo_energy[k][nocc:] for k in range(nkpts)]
nonzero_opadding, nonzero_vpadding = kmp2.padding_k_idx(mp, kind="split")
t2 = np.empty((nkpts,nkpts,nkpts,nocc,nocc,nvir,nvir), dtype=mo_coeff[0].dtype)
nao2mo = 0
for ki in range(nkpts):
orbo_i = mo_coeff[ki][:,:nocc]
for kj in range(ki, nkpts):
orbo_j = mo_coeff[kj][:,:nocc]
for ka in range(nkpts):
kb = mp.khelper.kconserv[ki, ka, kj]
if ki in k_ibz or kj in k_ibz or ka in k_ibz or kb in k_ibz:
nao2mo +=1
orbv_a = mo_coeff[ka][:,nocc:]
orbv_b = mo_coeff[kb][:,nocc:]
oovv = fao2mo((orbo_i,orbv_a,orbo_j,orbv_b),
(kpts[ki],kpts[ka],kpts[kj],kpts[kb]),
compact=False).reshape(nocc,nvir,nocc,nvir).transpose(0,2,1,3) / nkpts
eia = LARGE_DENOM * np.ones((nocc, nvir), dtype=mo_energy[0].dtype)
n0_ovp_ia = np.ix_(nonzero_opadding[ki], nonzero_vpadding[ka])
eia[n0_ovp_ia] = (mo_e_o[ki][:,None] - mo_e_v[ka])[n0_ovp_ia]
ejb = LARGE_DENOM * np.ones((nocc, nvir), dtype=mo_energy[0].dtype)
n0_ovp_jb = np.ix_(nonzero_opadding[kj], nonzero_vpadding[kb])
ejb[n0_ovp_jb] = (mo_e_o[kj][:,None] - mo_e_v[kb])[n0_ovp_jb]
eijab = lib.direct_sum('ia,jb->ijab',eia,ejb)
t2[ki,kj,ka] = np.conj(oovv / eijab)
logger.debug(mp, "Number of ao2mo transformations performed in KMP2: %d", nao2mo)
return t2
def _gamma1_intermediates(mp, t2=None):
if t2 is None:
t2 = mp.t2
if t2 is None:
t2 = make_t2_for_rdm1(mp)
nmo = mp.nmo
nocc = mp.nocc
nvir = nmo - nocc
kd = mp.kpts
nkpts = kd.nkpts
nkpts_ibz = kd.nkpts_ibz
dtype = t2.dtype
dm1occ = np.zeros((nkpts_ibz, nocc, nocc), dtype=dtype)
dm1vir = np.zeros((nkpts_ibz, nvir, nvir), dtype=dtype)
k_ibz = kd.ibz2bz
for ki in range(nkpts):
for kj in range(nkpts):
for ka in range(nkpts):
kb = mp.khelper.kconserv[ki, ka, kj]
t2a = t2[ki,kj,ka]
t2b = t2[ki,kj,kb]
if ki > kj:
t2a = t2[kj,ki,kb].transpose(1,0,3,2)
t2b = t2[kj,ki,ka].transpose(1,0,3,2)
if kb in k_ibz:
dm1vir[kd.bz2ibz[kb]] += einsum('ijax,ijay->yx', t2a.conj(), t2a) * 2 -\
einsum('ijax,ijya->yx', t2a.conj(), t2b)
if kj in k_ibz:
dm1occ[kd.bz2ibz[kj]] += einsum('ixab,iyab->xy', t2a.conj(), t2a) * 2 -\
einsum('ixab,iyba->xy', t2a.conj(), t2b)
return -dm1occ, dm1vir
[docs]
class KsymAdaptedKMP2(kmp2.KMP2):
[docs]
def kernel(self, mo_energy=None, mo_coeff=None, with_t2=WITH_T2):
if mo_energy is None: mo_energy = self.mo_energy
if mo_coeff is None: mo_coeff = self.mo_coeff
if mo_energy is None or mo_coeff is None:
logger.warn('mo_coeff, mo_energy are not given.\n'
'You may need to call mf.kernel() to generate them.')
raise RuntimeError
mo_coeff, mo_energy = kmp2._add_padding(self, mo_coeff, mo_energy)
# TODO: compute e_hf for non-canonical SCF
self.e_hf = self._scf.e_tot
self.e_corr, self.t2 = \
kernel(self, mo_energy, mo_coeff, verbose=self.verbose, with_t2=with_t2)
self.e_corr_ss = getattr(self.e_corr, 'e_corr_ss', 0)
self.e_corr_os = getattr(self.e_corr, 'e_corr_os', 0)
self.e_corr = float(self.e_corr)
self._finalize()
return self.e_corr, self.t2
make_rdm1 = make_rdm1
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def make_rdm2(self):
raise NotImplementedError
KRMP2 = KMP2 = KsymAdaptedKMP2
from pyscf.pbc import scf
scf.khf_ksymm.KRHF.MP2 = lib.class_as_method(KRMP2)
if __name__ == '__main__':
from pyscf.pbc import gto, scf, mp
cell = gto.Cell()
cell.atom='''
C 0.000000000000 0.000000000000 0.000000000000
C 1.685068664391 1.685068664391 1.685068664391
'''
cell.basis = 'gth-szv'
cell.pseudo = 'gth-pade'
cell.a = '''
0.000000000, 3.370137329, 3.370137329
3.370137329, 0.000000000, 3.370137329
3.370137329, 3.370137329, 0.000000000'''
cell.unit = 'B'
cell.verbose = 5
cell.build()
kpts = cell.make_kpts([2,2,2], space_group_symmetry=True)
kmf = scf.KRHF(cell, kpts=kpts, exxdiv=None)
ehf = kmf.kernel()
mymp = mp.KMP2(kmf)
emp2, t2 = mymp.kernel()
print(emp2 - -0.13314158977189)
