Title :

Assessing MP2 frozen natural orbitals in relativistic correlated electronic structure calculations

Author(s) :

Yuan, Xiang [Auteur]
Physico-Chimie Moléculaire Théorique [PCMT]
Department of Theoretical Chemistry and Amsterdam Centre for Multiscale Modeling (ACMM) VU University Amsterdam [ACMM]
Visscher, Lucas [Auteur]
Department of Theoretical Chemistry and Amsterdam Centre for Multiscale Modeling (ACMM) VU University Amsterdam [ACMM]
Severo Pereira Gomes, Andre [Auteur correspondant]
Physico-Chimie Moléculaire Théorique [PCMT]

Journal title :

The Journal of Chemical Physics

Pages :

224108

Publisher :

American Institute of Physics

Publication date :

2022-06-09

ISSN :

0021-9606

HAL domain(s) :

Chimie/Chimie théorique et/ou physique

English abstract : [en]

The high computational scaling with the number of correlated electrons and the size of the basis set is a bottleneck which limits applications of coupled cluster (CC) algorithms. This is particularly so for calculations ...
Show more >The high computational scaling with the number of correlated electrons and the size of the basis set is a bottleneck which limits applications of coupled cluster (CC) algorithms. This is particularly so for calculations based on 4-component relativistic Hamiltonians, which generally employ uncontracted basis sets and lead to large virtual molecular orbital (VMO) spaces. This problem may be alleviated by employing a more compact set of virtual spinors than those provided by the canonical Hartree-Fock (HF) set, such as those based on natural orbitals (NOs). In this paper we describe the implementation of a module for generating NOs for correlated wavefunctions, and in particular MP2 frozen natural orbitals (MP2FNOs), as a component of our novel implementation of relativistic coupled cluster theory for massively parallel architectures [J. Pototschnig et. al., J. Chem. Theory Comput. 17, 5509, 2021]. Our implementation is capable of manipulating both complex and quaternion density matrices, thus allowing for the generation of both Kramers-restricted and Kramers-unrestricted MP2FNOs. Furthermore, NOs are re-expressed in the parent atomic orbital (AO) basis, so that the code also makes it possible to generate CCSD natural orbitals in AO basis for further analysis. By investigating the truncation errors of MP2FNOs for both the correlation energy and molecular properties at CCSD level such as the electric field gradients at the nuclei (EFGs), electric dipole and quadrupole moments for hydrogen halides HX (X=F-Ts), and parity-violating energy differences (PV) for H$_2$Y$_2$ (Y=O-Se), we find that MP2FNOs accelerate the convergence of the correlation energy in a roughly uniform manner across the periodic table and that, with VMO spaces truncated to around half the size of the full spaces ones, it is possible to obtain reliable estimates for both energies and all molecular properties considered.Show less >

Language :

Anglais

Popular science :

Non

ANR Project :

Calcul de la diffusion inélastique résonante de rayons X pour toute la classification périodique
Physiques et Chimie de l'Environnement Atmosphérique
ULNE

Comment :

13 pages, 7 figures

Collections :

• Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM) - UMR 8523

Source :

Harvested from HAL