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PERFIK
National Physics Conference 2014 Venue :
Sunway Resort Hotel & Spa, Kuala Lumpur, Malaysia. Date :
18th – 19th November 2014 |
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Structural
Properties of Small Rhodium Clusters Yee Yeen Soona,
Thong
Leng Limb
and Tiem Leong Yoona a School of
Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia. b Faculty of
Engineering and Technology, Multimedia University, Melaka Campus, 75450
Melaka, Malaysia. Abstract. We report a
systematic study of the structural properties of rhodium clusters at
the atomistic level. A novel global-minimum search algorithm, known as
parallel tempering multicanonical basin hopping plus genetic algorithm
(PTMBHGA), is used to obtain the geometrical structures with lowest
minima at the semi-empirical level where
Gupta potential is used to describe the atomic interaction among the
rhodium atoms. These structures are then re-optimized at the density
functional theory (DFT) level with exchange-correlation energy
approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient
approximation (GGA). The structures are optimized for different spin
multiplicities. The ones with lowest energies will be taken as
ground-state structures. In most cases, we observe only minor changes
in the geometry and bond length of the clusters as a result of
DFT-level re-optimization. Only in some limited cases, the initial
geometries obtained from the PTMBHGA are modified by the
re-optimization. The variation of structural properties, such as
ground-state geometry, symmetry and binding energy, with respect to the
cluster size is studied and agreed well with other results available in
the literature. |
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Electronic
and Magnetic Properties of Small Rhodium Clusters Yee Yeen Soona, Tiem Leong Yoona
and Thong Leng Limb a School of
Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia. b
Faculty of Engineering and Technology, Multimedia University, Melaka
Campus, 75450 Melaka, Malaysia. Abstract. We
report a theoretical study of the electronic and magnetic properties of
rhodium-atomic clusters. The lowest energy structures at the
semi-empirical level of rhodium clusters are first obtained from a
novel global-minimum search algorithm, known as PTMBHGA, where Gupta
potential is used to describe the atomic interaction among the rhodium
atoms. The structures are then re-optimized at the density functional
theory (DFT) level with exchange-correlation energy approximated by
Perdew-Burke-Ernzerhof generalized gradient approximation. For the
purpose of calculating the magnetic moment of a given cluster, we
calculate the optimized structure as a function of the spin
multiplicity within the DFT framework. The resultant magnetic moments
with the lowest energies so obtained allow us to work out the magnetic
moment as a function of cluster size. Rhodium atomic clusters are found
to display a unique variation in the magnetic moment as the cluster
size varies. However, Rh4 and Rh6 are found to be nonmagnetic.
Electronic structures of the magnetic ground-state structures are also
investigated within the DFT framework. The results are compared against
those based on different theoretical approaches available in the
literature. |