Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analytical Gradient Theory for Strongly Contracted (SC-) and Partially
  Contracted (PC-) N-Electron Valence State Perturbation Theory (NEVPT2)   An analytical gradient theory for single-state N-electron valence state
perturbation theory (NEVPT2), using both strongly contracted (SC) and partially
contracted (PC) internal contraction schemes, is developed. We demonstrate the
utility of the developed algorithm in the optimization of the single-state
molecular geometry of acrolein, benzyne, benzene, the retinal chromophore PSB3,
the GFP chromophore pHBI, and porphine, with the cc-pVTZ basis sets. The
SC-NEVPT2 analytical gradients exhibit numerical instability due to the lack of
invariance with respect to the rotations among the inactive orbitals. On the
other hand, PC-NEVPT2 gives molecular geometries comparable to CASPT2 in any
tested cases. We discuss possible future developments that will make the NEVPT2
gradient algorithm a powerful tool for optimizing the molecular geometries and
conducting molecular dynamics simulations of correlated systems.

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The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom