MP2.py

import os
import numpy as np

from pyscf import mp
from pyscf.lib import logger

_pythonpath = os.environ['PYTHONPATH']

_present_in_pythonpath =  _pythonpath.find('iccsdn_module') >= 0

if (_present_in_pythonpath):
  import PostHF
else:
  from pyscf.iccsdn import PostHF

class MP2(object):
    def __init__(self, mf, nfo=0, nfv=0):

        self.mol  = mf.mol
        self.mf = mf
#       self.verbose = self.mol.verbose
#       self.stdout = self.mol.stdout

        self.nfo = nfo
        self.nfv = nfv

        self.nel = self.mol.nelectron
        
        self.e_hf = mf.e_tot

    def check_mp2(self, e_mp2):
        m = mp.MP2(self.mf)
        if abs(m.kernel()[0]-e_mp2) <= 1E-6:
            print("MP2 successfully done")
        else:
            print("MP2 energies differ")

    def calc_mp2_energy(self):

        e_mp2 = 2*np.einsum('ijab,ijab',self.t2,self.twoelecint_mo[:self.nocc,:self.nocc,self.nocc:self.nao,self.nocc:self.nao]) - np.einsum('ijab,ijba',self.t2,self.twoelecint_mo[:self.nocc,:self.nocc,self.nocc:self.nao,self.nocc:self.nao])
        print("MP2 correlation energy is : "+str(e_mp2))

        e_mp2_tot = self.e_hf + e_mp2
        print("MP2 energy is : "+str(e_mp2_tot))
	
        self.check_mp2(e_mp2)

    def run(self):

	#log = logger.Logger(self.stdout, self.verbose)
	#log.warn('**** RUNING MP2 ****')

        print('**** RUNING MP2 ****')

        AllData = PostHF.GetIntNData(self.mf, self.nfo, self.nfv)
        
        AllData.transform_all_ints()
        
        self.twoelecint_mo = AllData.twoelecint_mo
        
        self.nao = AllData.nao
        self.nocc = AllData.nocc
        self.nvirt = AllData.nvirt
        
        AllData.init_guess_t2()
        self.t2 = AllData.t2
        
        self.calc_mp2_energy()
        
        self.twoelecint_mo = None
        self.t2 = None

        print('**** MP2 is done ****')