Journal of Modern Physics, 2012, 3, 839-849
http://dx.doi.org/10.4236/jmp.2012.38110 Published Online August 2012 (http://www.SciRP.org/journal/jmp)
Electronic Structure with Rovibrational and Dipole
Moment Study of the NiO Molecule
Khalil Badreddine
1
, Nayla El-Kork
2
, Mahmoud Korek
1*
1
Faculty of Science, Beirut Arab University, Riad El Solh, Beirut, Lebanon
2
Khalifa University, Sharjah, UAE
Email:
*
fkorek@yahoo.com
Received June 10, 2012; revised July 9, 2012; accepted July 31, 2012
ABSTRACT
The potential energy curves have been investigated for the 40 lowest electronic states in the representation
below 25,000 cm
–1
of the molecule NiO via CASSCF, MRCI (single and double excitation with Davidson correction)
and CASPT2 methods. The harmonic frequency
2 1 s
e
, the internuclear distance r
e
, the rotational constant B
e
, the elec-
tronic energy with respect to the ground state T
e
, and the permanent dipole moment have been calculated. By using
the canonical functions approach, the eigenvalues E
v
, the rotational constant B
v
and the abscissas of the turning points
r
min
and r
max
have been calculated for the considered electronic states up to the vibration level v = 12. Eleven electronic
states have been studied theoretically here for the first time. The comparison of these values to the theoretical and ex-
perimental results available in literature shows a very good agreement.
Keywords: Ab Initio Calculation; NiO Molecule; Potential Energy Curves; Spectroscopic Constants; Dipole Moment;
Rovibrational Calculation
1. Introduction
The metal oxide NiO shows complicated electronic spec-
tra because of the presence of large number of electronic
states derived from several low-lying configurations but
it gives a systematic example of chemical bonding, which
depends on the relative energy between the 3d orbital of
the metal and the 2p orbital of oxygen [1,2]. The transi-
tion metal oxides have interesting applications in many
fields such as materials application and the oxidation of
metal surfaces. Among these compounds the NiO mole-
cule which is considered as a prototype of ionic crystals,
it is classified as a Mott-Hubbard insulator of very low
conductivity. The conductivity of nanostructred NiO was
found to be enhanced by six to eight orders of magnitude
over those of NiO single crystals [3-10]. The magnetic
properties of different sizes of NiO nanoparticles reveal
the presence of superparamagnetism as evidenced by the
increasing magnetization with decreasing size as well as
the magnetic hysteresis at low temperatures. Nanomag-
netism promises have applications in magnetic storage
with nanomagnetic particles, improved battery lifetimes
and also quantum computing [11-14]. The nanoarticles
formed by the NiO molecule have many applications in
electronics, optical, electro-optical devices and photo-
catalytic reaction. Despite this importance of the nickel
oxide NiO, this molecule has been studied experiment-
tally and theoretically [15-35] where a limited number of
electronic states have been obtained with the corre-
sponding molecular constants. The theoretical calculation
of the NiO molecule is an extreme computational chal-
lenge because of the degeneracy of several energetically
low-lying excited states and the open d, p, and s shells.
The presence of the d shell implies large multiplicities
which are split by spin-orbit interaction. The components
of the spin and the many states perturb each other. The
prediction and assignment of the electronic configuration
in the ground and excited states and the description of the
bonding may often be difficult.
Based on our previous theoretical calculation [36-45],
the important connection between energy relations of
solids and molecules [46], and stimulated by the lack of
theoretical calculation of excited electronic states with
the existence of preliminary experimental and theoretical
data, we performed an ab initio study of the low-lying
electronic states of the molecule NiO below 25,000 cm
–1
.
In this work, we investigate the potential energy curves
(PECs), the electric dipole moment and spectroscopic
constants for the 40
2s+1
Λ
(±)
low-lying electronic states of
this molecule obtained by MRCI and RSPT2 calculations.
Taking advantage of the electronic structure of the inves- *
Corresponding author.
Copyright © 2012 SciRes. JMP