arXiv subjects

T. A. Isaev

Publications and source records attributed to T. A. Isaev.

22 records · Page 2Linked to original sources

arXiv2004

In search of the electron dipole moment: Ab initio calculations on ^207PbO excited states

We report ab initio correlated relativistic calculations of the effective electric field W_d acting on the electron in two excited electronic states of PbO, required for extracting the electric dipole moment of the electron from an ongoing experiment at Yale, which has the potential of improving accuracy for this elusive property by several orders of magnitude. The generalized relativistic effective core potential and relativistic coupled cluster methods are used, followed by nonvariational one-center restoration of the four-component wavefunction in the heavy atom core. W_d is -3.2\times 10^24 Hz/ecm for the a(1) state and -9.7\times 10^24 Hz/ecm for the B(1) state. Comparison of calculated and experimental values of the hyperfine constant A_{\parallel} provides an accuracy check for the calculation.

physics.atom-ph↗

arXiv2003

Accuracy and efficiency of modern methods for electronic structure calculation on heavy- and superheavy-element compounds

The methods which are actively used for electronic structure calculations of low-lying states of heavy- and superheavy-element compounds are briefly described. The advantages and disadvantages of calculations with the Dirac-Coulomb-Breit Hamiltonian, Huzinaga-type pseudopotential, shape-consistent Relativistic Effective Core Potential (RECP) and Generalized RECP are discussed. The nonvariational technique of the electronic structure restoration in atomic cores after the RECP calculation of a molecule is presented. The features of some approaches accounting for electron correlation, the configuration interaction and coupled cluster methods, are also described. The results of calculations on E113, E114, U and other heavy-atom systems are presented.

physics.chem-ph↗

arXiv2002

Calculation of $P_ and $T_ odd effects in $"" sup 205_TIF including electron correlation

A method and codes for two-step correlation calculation of heavy-atom molecules have been developed, employing the generalized relativistic effective core potential and relativistic coupled cluster (RCC) methods at the first step, followed by nonvariational one-center restoration of proper four-component spinors in the heavy cores. Electron correlation is included for the first time in an ab initio calculation of the interaction of the permanent P,T-odd proton electric dipole moment with the internal electromagnetic field in a molecule. The calculation is performed for the ground state of TlF at the experimental equilibrium, R_e=2.0844 A, and at R=2.1 A, with spin-orbit and correlation effects included by RCC. Calculated results with single cluster amplitudes only are in good agreement (3% and 1%) with recent Dirac-Hartree-Fock (DHF) values of the magnetic parameter M; the larger differences occurring between present and DHF volume parameter (X) values, as well as between the two DHF calculations, are explained. Inclusion of electron correlation by GRECP/RCC with single and double excitations has a major effect on the P,T-odd parameters, decreasing M by 17% and X by 22%.

physics.chem-ph↗

arXiv2001

GRECP/5e-MRD-CI calculation of the electronic structure of PbH

The correlation calculation of the electronic structure of PbH is carried out with the Generalized Relativistic Effective Core Potential (GRECP) and MultiReference single- and Double-excitation Configuration Interaction (MRD-CI) methods. The 22-electron GRECP for Pb is used and the outer core 5s, 5p and 5d pseudospinors are frozen using the level-shift technique, so only five external electrons of PbH are correlated. A new configuration selection scheme with respect to the relativistic multireference states is employed in the framework of the MRD-CI method. The [6,4,3,2] correlation spin-orbit basis set is optimized in the coupled cluster calculations on the Pb atom using a recently proposed procedure, in which functions in the spin-orbital basis set are generated from calculations of different ionic states of the Pb atom and those functions are considered optimal which provide the stationary point for some energy functional. Spectroscopic constants for the two lowest-lying electronic states of PbH ($^2Π_{1/2}, ^2Π_{3/2}$) are found to be in good agreement with the experimental data.

physics.chem-ph↗