| dc.description | Transition metal oxides semiconductors (TMOs) are known for their special optical and electrical
properties with wide-ranging applications, including gas sensing, storage devices such as Li-ion
batteries, solar cells, and catalysts[1,2]. Among different types of TMOs, there is a class of materials
that are distinguished by their unique layered structure and multiple oxidation states, such as MoO3,
WO3, and V2O5. The molybdenum trioxide (MoO3) is known for its photo-, thermo- and electrochromism,
high catalytic activity[3]. The MoO3 has found in different structural phases including
the orthorhombic phase, ??-MoO3; monoclinic phase, ??-MoO3; metastable phase at high-pressure
conditions, ?????-MoO3; and hexagonal phase, h-MoO3[4]. Among them, the ??-MoO3 is the most stable crystal phase and it has a layered structure consisting of van der Waals bonded sheets of distorted
edge-sharing Mo???O6 octahedra in which Mo atoms are bounded by three distinct types of oxygen
atoms[5].
In this research, the structural properties and hyperfine parameters of 111mCd(111Cd) impurities
in ??-MoO3 are investigated by first-principle calculations in the framework of density functional
theory (DFT). The Perdew???Burke???Ernzerh of generalized gradient approximation (GGA-PBE), and
GGA-PBE plus Hubbard-U corrections for onsite Coulomb interactions are used in the DFT calculations.
In the calculations performed, the effect of van der Waals forces between layers is employed
using the DFT-D3 method[6]. To interpret the experimental results, different configurations around
the Cd atom including the different types of oxygen vacancies are simulated. The comparison of experimental
data with calculated hyperfine parameters indicates that the Cd atom is predominantly
located in the interstitial lattice site of MoO3, and also the oxygen vacancy is most likely to form on
the 2-fold coordinated (O2) atoms.
The results of this work demonstrate the benefit of first-principle calculations for solving the outstanding
questions arising from the experiment. | |
