The optical properties of the tetragonal phase of BaTiO ₃ have been studied using density functional methods, applying the generalized gradient approximation at room temperature and a hybrid functional for static lattice analysis.

Structural, electronic, and magnetic properties of Mn₂Co_1-xV_xZ (Z = Ga, Al, x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys were theoretically investigated for the case of L2₁ (space group Fm$\overline{3}$m), L2_1b (L2₁ structure with partial disordering between Co and Mn atoms) and XA (space group F$\overline{4}$3m) structures. It was found that the XA structure is more stable at low V concentrations, while the L2₁ structure is energetically favorable at high V concentrations. A transition from L2₁ to XA ordering occurs near x = 0.5, which qualitatively agrees with the experimental results. Comparison of the energies of the L2_1b and XA structures leads to the fact that the phase transition between these structures occurs at x = 0.25, which is in excellent agreement with the experimental data. The lattice parameters linearly change as x grows. For the L2₁ structure, a slight decrease in the lattice constant a was observed, while for the XA structure, an increase in a was found. The experimentally observed nonlinear behavior of the lattice parameters with a change in the V content is most likely a manifestation of the presence of a mixture of phases. Almost complete compensation of the magnetic moment was achieved for the Mn₂Co_1-xV_xZ alloy (Z = Ga, Al) at x = 0.5 for XA ordering. In the case of the L2₁ ordering, it is necessary to consider a partial disorder of atoms in the Mn and Co sublattices in order to achieve compensation of the magnetic moment.

First-principles calculations of the stability, electronic, and magnetic properties of full-Heusler compound V₂FeSi and Fe₂VSi in regular ($L{2}_1$) and inverse ($XA$) structures have been performed using density functional theory within an SCAN meta-GGA functional. It is found that the $XA$ crystal lattice is energetically more favorable for V₂FeSi, while Fe₂VSi forms the $L{2}_1$ structure. In both cases, the electronic structure of the energetically stable modifications corresponds to half-metallic ferrimagnets. Magnetic properties of energetically favorable structures obey the Slater–Pauling rule. All considered properties of the studied structures are explained within the crystal orbital Hamilton population analysis.

A classical molecular dynamics simulation of cation diffusion in isolated crystals (U_xPu_yTh_1−x−y)O₂ bounded by a free surface was performed. It was shown that in the bulk of the same model crystallite, the diffusion coefficients of cations of all types were practically identical. At the same time, the cation diffusion coefficients changed with the melting temperature of nanocrystals, which increased with increasing thorium content. At a given temperature, the diffusion coefficients were the higher, the lower were the melting points of the (U_xPu_yTh_1−x−y)O₂ crystallites. The temperature dependences of the diffusion coefficients in crystallites of different compositions converged when using coordinates normalized to the melting points.

This research investigates the structural, electronic, mechanical, and vibrational properties of double half-Heusler compounds with the generic formula Ti2Pt2ZSb (Z = Al, Ga, and In) using density functional theory calculations. The generalized gradient approximation within the Perdew-Burke-Ernzerhof functional was employed for structural optimization and the hybrid HSE06 functional for electronic properties. Our results demonstrate that these compounds are energetically favorable, dynamically and mechanically stable. Electronic structure calculations reveal that Ti2Pt2AlSb double half-Heusler compound is a non-magnetic semiconductor with an indirect bandgap of 1.49 eV, while Ti2Pt2GaSb and Ti2Pt2InSb are non-magnetic semiconductors with direct bandgaps of 1.40 eV. The alloys exhibit low lattice thermal conductivity (2.35–2.66 W/mK) and high melting temperature (1211–1248 K), making them promising candidates for high-technological applications. Further performed analysis, including phonon dispersion curves, electron localization function (ELF), and Bader charge analysis, provides insights into the bonding character and vibrational properties of these materials.