Finite-order method to calculate approximate density matrices in the Fock-space multireference coupled cluster theory

Abstract

An efficient approach to calculate approximate pure-state and transition reduced density matrices in the framework of the multireference relativistic Fock-space coupled cluster (FS CC) theory is proposed. The method is based on the effective operator formalism and consists of the direct substitution of the FS CC Ansatz for a wave operator into the effective operator expression with the subsequent truncation of expansion at the terms quadratic in cluster amplitudes. The final density matrix is defined by active-space density matrices of different ranks "dressed" with contributions from cluster operators. The method gives a connected expression for pure-state density matrices, provided that the intermediate normalization condition is fulfilled. Moreover, under some additional assumptions, the connectivity can also be ensured for calculated transition property matrix elements and natural transition spinors. The developed technique allows for fast and accurate calculations of one-particle reduced density matrices for a wide range of electronic states. A pilot application of the new technique to construct averaged atomic natural orbital (ANO) basis sets for fully relativistic electronic structure calculations is presented.

References in corpus (13)

• Combined 4-component and relativistic pseudopotential study of ThO for the electron electric dipole moment search
• Theoretical study of thorium monoxide for the electron electric dipole moment search, II: Electronic properties of $H^3{\Delta }_1$ in ThO
• Opportunities for Fundamental Physics Research with Radioactive Molecules
• Concept of effective states of atoms in compounds to describe properties determined by the densities of valence electrons in atomic cores
• Approaching meV level for transition energies in the radium monofluoride molecule RaF and radium cation Ra${}^{+}$ by including quantum-electrodynamics effects
• Nuclear charge radii of silicon isotopes
• Relativistic Fock space coupled cluster study of bismuth electronic structure to extract the Bi nuclear quadrupole moment
• Accurate \textit{ab initio} calculations of RaF electronic structure indicate the need for more laser-spectroscopical measurements
• Laser-coolable AcOH${}^{+}$ ion for $\mathcal{C}\mathcal{P}$-violation searches
• Theoretical molecular spectroscopy of actinide compounds: The ThO molecule
• Compound-tunable embedding potential method to model local electronic excitations on $f$-element ions in solids: Pilot relativistic coupled cluster study of Ce and Th impurities in yttrium orthophosphate, YPO${}_4$
• Ab initio study of electronic states and radiative properties of the AcF molecule
• Optical cycling in charged complexes with Ra-N bonds

Cited by in corpus (1)

• On the rank-reduced relativistic coupled cluster method