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Title: Investigation of Pure and Doped Actinide Monopnictides by using DFT
Authors: Siddique, Muhammad
Keywords: Physical Sciences
Issue Date: 2020
Publisher: The University of Lahore, Lahore.
Abstract: Thorium pnictides deserve a considerable research attention in view of their fundamental and technological role in science. The present work is focused on density functional-theory (DFT) based first-principles calculations of doped and undoped cubic thorium monopnictides compounds, i.e., ThX (X=N ,P ,As ,Sb and Bi ), for their structural, electrical, thermoelectric and magnetic properties both in ambient conditions and at high pressures. The full potential linearized augumented plane wave (FP-LAPW) + local orbital (lo) method is employed within PBEsol, LSDA, WC-GGA and PBE-GGA corrections both for minority and majority spin polarizations. Besides, the DFT+U model was also invoked for the investigation of correlation affects of 5f–states of thorium actinide to better investigate the electronic and magnetic properties of the monopnictides. The structural properties including the equilibrium volume and energy, lattice parameters, bulk modulus and its pressure derivative, and bond lengths were investigated by fitting the total energy for the optimized unit-cell volume of the compounds using Murnaghan’s equation of state with both spin channels. The electronic and magnetic properties calculated from optimized structures of the compounds include total and partial densities of states, energy band structure and spin magnetic moments. Whereas the calculated thermoelectric properties include thermal and electrical conductivities, See beck coefficient, power factor and figure of merit by employing semi- classical Boltzman’s theory for the thorium mono-pnictides compounds. The thorium mono-pnictides compounds are found to be stable in metallic non magnetic states having small values of thermoelectric figure of merit in ambient conditions. The carbon doping has considerably increased the metallic characteristics of ThN by accumulating electrons population below and above the Fermi level by enhancing the overlapping of carbon states with 5f states of Th. There is a fluctuation of spin magnetic moments with carbon doping concentration. Sign flipping of spin magnetic moments from positive to negative and vice versa is also observed at various pressures, which may arise from the alteration spin orientations of the electrons with respect to angular momentum direction. In conformation to the earlier studies, the thorium mono-pnictides show non-magnetic metallic character. These compounds may be potential candidates for applications in electronic, thermo-electric and nuclear reactor devices.
Gov't Doc #: 21286
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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