First principles calculation of thermo-mechanical properties of thoria using Quantum ESPRESSO

Abstract

In this work, we have used Quantum ESPRESSO (QE), an open source first principles code, based on density-functional theory, plane waves, and pseudopotentials, along with quasi-harmonic approximation (QHA) to calculate the thermo-mechanical properties of thorium dioxide (ThO[Formula: see text]. Using Python programming language, our group developed qe-nipy-advanced, an interface to QE, which can evaluate the structural and thermo-mechanical properties of materials. We predicted the phonon contribution to thermal conductivity ([Formula: see text] using the Slack model. We performed the calculations within local density approximation (LDA) and generalized gradient approximation (GGA) with the recently proposed version for solids (PBEsol). We employed a Monkhorst-Pack [Formula: see text] k-points mesh in reciprocal space with a plane wave cut-off energy of 150 Ry to obtain the convergence of the structure. We calculated the dynamical matrices of the lattice on a [Formula: see text] mesh. We have predicted the heat capacity, thermal expansion and the phonon contribution to thermal conductivity, as a function of temperature up to 1400[Formula: see text]K, and compared them with the previous work and known experimental results.

Accident tolerant composite nuclear fuels

“…We also found previously [9,10] that new generalized gradient approximation (GGA) functional for solids, PBEsol used with the pseudopotentials generated for PBE or PBEsol functional lead to equilibrium lattice constants that agree very well with experiment and therefore it is used here in our new calculations. Equally good results are obtained with local density approximation (LDA) and norm conserved pseudopotentials which we have been used predominantly in our previous calculations [10].…”

“…QE is a first principles code using density functional theory, plane waves and pseudopotentials; and it can predict ground state material properties in agreement with experiment provided the parameters like plane wave cutoff energies, k point optimal mesh and equilibrium structure are optimized accurately as described earlier [10]. We also found previously [9,10] that new generalized gradient approximation (GGA) functional for solids, PBEsol used with the pseudopotentials generated for PBE or PBEsol functional lead to equilibrium lattice constants that agree very well with experiment and therefore it is used here in our new calculations. Equally good results are obtained with local density approximation (LDA) and norm conserved pseudopotentials which we have been used predominantly in our previous calculations [10].…”

“…Slack also noted the correlation between the lattice thermal conductivity value and the Debye temperature [5]. We used here generalised Slack model, where we include contribution to the thermal conductivity from both acoustic and optical phonons and all inputs to the model are calculated as described previously [4,10] and above. Slack model predicts large thermal conductivity for both BP and BAs and BP may be considered for a future application provided it has a proper isotopic contribution that is not absorbing neutrons.…”

Structural and electronic properties of the iron pnictide compound EuFe2As2 from first principles

“…In our study, we used the Plane Wave method to investigate the electronic and mechanical structure properties of EuFe As 2 2 from first principles, using the open source computer code Quantum Espresso [22][23][24][25]. Self -Consistent Calculations were run to obtain the total and Fermi energy of the system, which is a useful parameter in describing the electronic structure properties of the compound [26].…”

The generalized quasiharmonic approximation via space group irreducible derivatives

“…The ground state crystal structure of thoria is the flourite structure, which has space group F m3m (225). A number of studies have used ab initio methods to predict finite temperature properties of tho-ria [31][32][33][34][35][36][37], however there is limited experimental data available for comparison. While there have been multiple studies on thermal expansion [38][39][40][41], there are only two studies that measured the elastic constants of thoria at room temperature [42,43].…”