scholarly journals Thermodynamics of Plutonium Monocarbide from Anharmonic and Relativistic Theory

2020 ◽  
Vol 10 (18) ◽  
pp. 6524
Author(s):  
Per Söderlind ◽  
Alexander Landa ◽  
Aurélien Perron ◽  
Emily E. Moore ◽  
Christine Wu
Keyword(s):  
Experimental Data ◽  
Electronic Structure ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Spin Orbit ◽  
Functional Theory ◽  
Gibbs Energies ◽  
Anharmonic Lattice ◽  
5F Electrons

Thermodynamics of plutonium monocarbide is studied from first-principles theory that includes relativistic electronic structure and anharmonic lattice vibrations. Density-functional theory (DFT) is expanded to include orbital-orbital coupling in addition to the relativistic spin-orbit interaction for the electronic structure and it is combined with anharmonic, temperature dependent, lattice dynamics derived from the self-consistent ab initio lattice dynamics (SCAILD) method. The obtained thermodynamics are compared to results from simpler quasi-harmonic theory and experimental data. Formation enthalpy, specific heat, and Gibbs energy calculated from the anharmonic model are validated by direct comparison with a calculation of phase diagram (CALPHAD) assessment of PuC and sub-stochiometric PuC0.896. Overall, the theory reproduces CALPHAD results and measured data for PuC rather well, but the comparison is hampered by the sub-stoichiometric nature of plutonium monocarbide. It was found that a bare theoretical approach that ignores spin-orbit and orbital-orbital coupling (orbital polarization) of the plutonium 5f electrons promotes too soft phonons and Gibbs energies that are incompatible with that of the CALPHAD assessment of the experimental data. The investigation of PuC suggests that the electronic structure is accurately described by plutonium 5f electrons as “band like” and delocalized, but correlate through spin polarization, orbital polarization, and spin-orbit coupling, in analogy to previous findings for plutonium metal.

scholarly journals Stability and electronic structure of magnesium hydride and magnesium deuteride under high pressure

2021 ◽  
Vol 2145 (1) ◽  
pp. 012026
Author(s):  
Chayaphon Boonchot ◽  
Prutthipong Tsuppayakorn-Aek ◽  
Udomsilp Pinsook ◽  
Thiti Bovornratanaraks
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
High Pressure ◽  
Electronic Structure ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Band Structures ◽  
Functional Theory ◽  
Superconducting Metal ◽  
Quantum Espresso

Abstract Metal polyhydrides have attracted considerable attention because some of them become a metal under high pressure, and some undergo a phase transition into a superconductor. Some superconducting metal polyhydrides have recently been discovered with a high value of critical temperature (Tc) under pressure. In this research, we calculated the structures of MgH2, MgH3 and MgD3 under pressure between 0-300 GPa in order to determine the formation enthalpy and electronic property of their structures under high pressure by using density functional theory (DFT) based on the Quantum Espresso code. We found that the band structures reveal the metallic character of the compounds under high pressure. The energy band structures of MgHx and MgDx are exactly the same. However, their phonon dispersions are different due to the so-called isotope effect. We determined the composition stability by using the convex hull of Mg, H and the compounds. We found that MgH3 becomes thermodynamically more stable than MgH2 at around 150 GPa. The results of phonons confirm that they are dynamically stable. This finding is served as a basis for future superconducting calculations.

Electronic structure and spectroscopy of homoleptic compounds of dimolybdenum using TDDFT

2016 ◽  
Vol 94 (1) ◽  
pp. 20-27
Author(s):  
Pere Vilarrubias
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Molecular Orbitals ◽  
Time Dependent ◽  
Electronic Transitions ◽  
Functional Theory ◽  
Dependent Density ◽  
Good Agreement

Ten compounds of dimolybdenum are studied using density functional theory and time-dependent density functional theory. The energy of the strongest symmetry-allowed bands is calculated. The results are then compared with experimental data, when available. The PW91 functional gives results for geometry and for the energy of the δ→δ* band that show good agreement with experimental data. However, the B3LYP functional gives more realistic values for the whole spectrum when the results are compared with experimental data. Finally, the different values of energy of these bands are explained analyzing the molecular orbitals involved in these transitions. Some ligands can act as an unsaturated system in conjugation with the delta bond, modifying the energies of the electronic transitions.

scholarly journals Thermodynamics of technetium: reconciling theory and experiment using density functional perturbation analysis

2015 ◽  
Vol 44 (28) ◽  
pp. 12735-12742 ◽  
Author(s):  
Philippe F. Weck ◽  
Eunja Kim
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Thermodynamic Properties ◽  
Perturbation Analysis ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Functional Theory ◽  
Theory And Experiment

The structure, lattice dynamics and thermodynamic properties of bulk technetium were investigated within the framework of density functional theory. The predicted thermal expansion and isobaric heat capacity are in excellent agreement with available experimental data.

First-principles study on the electronic structure and elastic properties of Mo2NiB2 doped with V

2018 ◽  
Vol 32 (10) ◽  
pp. 1850065 ◽  
Author(s):  
Jinming Li ◽  
Xiaobo Li ◽  
Haiyun Gao ◽  
Dian Peng
Keyword(s):  
Electronic Structure ◽  
Elastic Properties ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Formation Enthalpy ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Ternary Boride

The content of this study is to analyze the electronic structure and elastic properties that the different structures of Mo2NiB2 and doping with V of the tetragonal M3B2 (Mo2Ni[Formula: see text]V[Formula: see text]B2 and Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2) (x = 0.25, 0.5, 0.75 and y = 0.125, 0.25, 0.375) by first-principles calculations based on density functional theory (DFT) combined with the projection-plus-wave method. But the calculated formation energy shows that V atoms prefer to substitute the Mo and Ni atoms of the tetragonal Mo2NiB2. Moreover, with the increase of V content, the formation enthalpy of tetragonal Mo2NiB2 is reduced, and the formation enthalpy of Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2 is the least as −53.23 kJ/mol. The calculated elastic constant suffices the condition of mechanical stability, indicate that they are stable. The calculated elastic modulus illustrates that Mo2NiB2 having better mechanical properties when V elements are at Mo and Ni sites instead of Ni sites. The calculated and analyzed density of states of Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2 has the smallest the density of states at the Fermi level indicating that it has the more stable structure. For the theoretical analysis of the first-principles calculations, the addition of 15 atom% of the V and V doping modes of Mo and Ni are preferentially replaced by V atoms of Mo2NiB2 ternary boride has the best performance.

Doping effects on the geometric and electronic structure of tin clusters

2019 ◽  
Vol 21 (44) ◽  
pp. 24478-24488 ◽  
Author(s):  
Martin Gleditzsch ◽  
Marc Jäger ◽  
Lukáš F. Pašteka ◽  
Armin Shayeghi ◽  
Rolf Schäfer
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Beam Deflection ◽  
Functional Theory ◽  
Doping Effects ◽  
Depth Analysis ◽  
Trajectory Simulations

In depth analysis of doping effects on the geometric and electronic structure of tin clusters via electric beam deflection, numerical trajectory simulations and density functional theory.

scholarly journals Influence of Copper(I) Halides on the Reactivity of Aliphatic Carbodiimides

2020 ◽  
Vol 3 (1) ◽  
pp. 20
Author(s):  
Valentina Ferraro ◽  
Marco Bortoluzzi
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
General Formula ◽  
Electron Density ◽  
Density Functional ◽  
Functional Theory ◽  
Fukui Functions ◽  
Bond Lengths ◽  
Linear Complexes ◽  
Nitrogen Bond

The influence of copper(I) halides CuX (X = Cl, Br, I) on the electronic structure of N,N′-diisopropylcarbodiimide (DICDI) and N,N′-dicyclohexylcarbodiimide (DCC) was investigated by means of computational DFT (density functional theory) methods. The coordination of the considered carbodiimides occurs by one of the nitrogen atoms, with the formation of linear complexes having a general formula of [CuX(carbodiimide)]. Besides varying the carbon–nitrogen bond lengths, the thermodynamically favourable interaction with Cu(I) reduces the electron density on the carbodiimides and alters the energies of the (NCN)-centred, unoccupied orbitals. A small dependence of these effects on the choice of the halide was observable. The computed Fukui functions suggested negligible interaction of Cu(I) with incoming nucleophiles, and the reactivity of carbodiimides was altered by coordination mainly because of the increased electrophilicity of the {NCN} fragments.

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