TY - JOUR

T1 - Two-step method for precise calculation of core properties in molecules

AU - Titov, A. V.

AU - Mosyagin, N. S.

AU - Petrov, A. N.

AU - Isaev, T. A.

PY - 2005/8/5

Y1 - 2005/8/5

N2 - Precise calculations of core properties in heavy-atom systems that are described by the operators heavily concentrated in atomic cores, such as hyperfine structure and P,T-parity nonconservation effects, require accounting for relativistic effects. Unfortunately, four-component calculation of molecules containing heavy elements is very consuming already at the stages of calculation and transformation of two-electron integrals with a basis set of four-component spinors. In turn, the relativistic effective core potential (RECP) calculations of valence (spectroscopic, chemical, etc.) properties of molecules are very popular, because the RECP method allows one to treat quite satisfactorily the correlation and relativistic effects for the valence electrons of a molecule and to reduce significantly the computational efforts. The valence molecular spinors are usually smoothed in atomic cores, and, as a result, direct calculation of electronic densities near heavy nuclei is impossible. In this paper, the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component RECP calculation of a molecule are discussed. Their efficiency is illustrated in correlation calculations of hyperfine structure and parity nonconservation effects in heavy-atom molecules YbF, BaF, TIF, and PbO.

AB - Precise calculations of core properties in heavy-atom systems that are described by the operators heavily concentrated in atomic cores, such as hyperfine structure and P,T-parity nonconservation effects, require accounting for relativistic effects. Unfortunately, four-component calculation of molecules containing heavy elements is very consuming already at the stages of calculation and transformation of two-electron integrals with a basis set of four-component spinors. In turn, the relativistic effective core potential (RECP) calculations of valence (spectroscopic, chemical, etc.) properties of molecules are very popular, because the RECP method allows one to treat quite satisfactorily the correlation and relativistic effects for the valence electrons of a molecule and to reduce significantly the computational efforts. The valence molecular spinors are usually smoothed in atomic cores, and, as a result, direct calculation of electronic densities near heavy nuclei is impossible. In this paper, the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component RECP calculation of a molecule are discussed. Their efficiency is illustrated in correlation calculations of hyperfine structure and parity nonconservation effects in heavy-atom molecules YbF, BaF, TIF, and PbO.

KW - Ab initio molecular calculation

KW - Atom in a molecule

KW - Electronic structure

KW - Molecules with heavy atoms

KW - One-center restoration

KW - Relativistic effective core potential

UR - http://www.scopus.com/inward/record.url?scp=23144456322&partnerID=8YFLogxK

U2 - 10.1002/qua.20418

DO - 10.1002/qua.20418

M3 - Article

AN - SCOPUS:23144456322

VL - 104

SP - 223

EP - 239

JO - International Journal of Quantum Chemistry

JF - International Journal of Quantum Chemistry

SN - 0020-7608

IS - 2 SPEC. ISS.

ER -