2,556 research outputs found
Relativistic equation-of-motion coupled-cluster method for the electron attachment problem
The article considers the successful implementation of relativistic
equation-of-motion coupled cluster method for the electron attachment problem
(EA-EOMCC) at the level of single- and double- excitation approximation. The
implemented relativistic EA-EOMCC method is employed to calculate ionization
potential values of alkali metal atoms (Li, Na, K, Rb, Cs, Fr) and the vertical
electron affinity values of LiX (X = H, F, Cl, Br), NaY (Y = H, F, Cl) starting
from their closed-shell configuration. Both four-component and exact
two-component calculations are done for all the opted systems. Further, we have
shown the effect of spin-orbit interaction considering the atomic systems. The
results of our atomic calculations are compared with the values from the NIST
database and the results are found to be very accurate (< 1 %).Comment: 26 Pages, 3 figures, 6 Tables. Comments are welcom
Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: Atoms Hg and Pb and their compounds
A way to account for correlations between the chemically active (valence) and
innermore (core) electrons in the framework of the generalized relativistic
effective core potential (GRECP) method is suggested. The "correlated" GRECP's
(CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the
external twelve and four electrons of them, correspondingly, should be treated
explicitly in the subsequent calculations with these CGRECP's whereas the
innermore electrons are excluded from the calculations. Results of atomic
calculations with the correlated and earlier GRECP versions are compared with
the corresponding all-electron Dirac-Coulomb values. Calculations with the
above GRECP's and CGRECP's are also carried out for the lowest-lying states of
the HgH molecule and its cation and for the ground state of the PbO molecule as
compared to earlier calculations and experimental data. The accuracy for the
vibrational frequencies is increased up to an order of magnitude and the errors
for the bond lengths (rotational constants) are decreased in about two times
when the correlated GRECP's are applied instead of earlier GRECP versions
employing the same innercore-outercore-valence partitioning.Comment: 12 pages, 4 tables, the text of the paper was significantly improve
Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory
Here, we review the historical development, current status, and prospects of
Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only
theory.Comment: 15 page
A New Approach To Relativistic Gaussian Basis Functions: Theory And Applications
We present a new hybrid method to solve the relativistic Hartree-Fock-Roothan
equations where the one- and two-electron radial integrals are evaluated
numerically by defining the basis functions on a grid. This procedure reduces
the computational costs in the evaluation of two-electron radial integrals. The
orbitals generated by this method are employed to compute the ionization
potentials, excitation energies and oscillator strengths of alkali-metal atoms
and elements of group IIIA through second order many-body perturbation theor
and other correlated theories.Comment: RevTex (15 pages) one figur
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