26. mrpt — Multi-reference perturbation theory

26.1. N-electron valance perturbation theory (NEVPT2)

class pyscf.mrpt.nevpt2.NEVPT(mc, root=0)[source]

Strongly contracted NEVPT2

Attributes:
root
: int
To control which state to compute if multiple roots or state-average wfn were calculated in CASCI/CASSCF
compressed_mps
: bool
compressed MPS perturber method for DMRG-SC-NEVPT2

Examples:

>>> mf = gto.M('N 0 0 0; N 0 0 1.4', basis='6-31g').apply(scf.RHF).run()
>>> mc = mcscf.CASSCF(mf, 4, 4).run()
>>> NEVPT(mc).kernel()
-0.14058324991532101
compress_approx(maxM=500, nevptsolver=None, tol=1e-07, stored_integral=False)[source]

SC-NEVPT2 with compressed perturber

Kwargs :
maxM
: int
DMRG bond dimension

Examples:

>>> mf = gto.M('N 0 0 0; N 0 0 1.4', basis='6-31g').apply(scf.RHF).run()
>>> mc = dmrgscf.DMRGSCF(mf, 4, 4).run()
>>> NEVPT(mc, root=0).compress_approx(maxM=100).kernel()
-0.14058324991532101
load_ci(root=None)[source]

Hack me to load CI wfn from disk