We present a first-principles investigation of the combined effects of chemical doping and nanostructuring on the thermoelectric performance of the double halide perovskite Cs 2 NaYbCl 6 . Using density functional theory and Boltzmann transport calculations, we explicitly include all relevant scattering mechanisms (namely, electron–phonon, phonon–phonon, Coulomb impurity, phonon–impurity, and grain boundary scattering) to evaluate electrical and thermal transport coefficients. Our results show that Coulomb scattering from dopants is strongly screened and negligible compared to dominant electron–phonon interactions. Thus, both n - and p -type doping enhance electrical conductivity while only moderately reducing the Seebeck coefficient, leading to a significant increase in power factor. Phonon–impurity scattering is found to be minimal, while grain boundary scattering effectively reduces lattice thermal conductivity without strongly affecting carrier mobility. Combining optimal n -type doping ( 10 19 cm − 3 ) with nanoscale grains (10 nm), the figure of merit Z T increases from ∼ 10 − 8 in the pristine crystal to ∼ 0.12 . These findings demonstrate a viable pathway for improving thermoelectric efficiency in wide-band-gap, lead-free perovskites through controlled extrinsic modifications.

Using a b i n i t i o density functional theory (DFT) calculations, we investigate the electronic structure, phase stability, and magnetic properties of equiatomic binary alloys between Al and 3 d magnetic transition elements (Cr, Mn, Fe, Co, and Ni). Thermodynamically, all five binary aluminides are more stable in the ordered B2 phase than in the disordered body-centered-cubic phase, and Co is found to be the strongest B2 forming element with Al. The AlCo and AlNi compounds with B2 structure are verified to be nonmagnetic, whereas AlFe turns out to be weakly magnetic, which is consistent with other DFT calculations employing similar exchange-correlation approximations. Magnetic simulations based on the Heisenberg Hamiltonian predict an antiferromagnetic ground state for the hypothetical B2 AlCr, which is also confirmed by direct DFT calculations. Doping AlCr with Co leads to an antiferromagnetic-to-ferromagnetic transition, where ferromagnetism is to a large extent attributed to Cr atoms. The phase stability and magnetic trends are explained using electronic structure arguments. The present findings contribute to a deeper understanding of the phase stability and magnetic properties of Al binary alloys, providing insights into the formation mechanisms of the B2 structure with 3 d magnetic transition metals.

We report the successful growth of stoichiometric, epitaxial ytterbium nitride (YbN) thin films via molecular beam epitaxy under ultrahigh vacuum conditions using activated nitrogen supplied by a plasma source. Through systematic optimization of the growth parameters, we achieved high-quality YbN films with excellent crystallinity and a well-defined (100) out-of-plane orientation on MgO(100) and LaAlO 3 (100) substrates, as determined by reflection high-energy electron diffraction and x-ray diffraction. In photoelectron spectroscopy results unambiguously demonstrate the semiconducting character of YbN and the fully trivalent valence state of the Yb ions. Using the photon-energy dependence of the valence band spectra we were able to reveal a significant hybridization between the Yb 4 f and N 2 p states.

We propose a computational scheme for the diffusion and retention of multiple hydrogen isotopes (HI) with multi-occupancy traps parametrized by first principles calculations. We show that it is often acceptable to reduce the complexity of the coupled differential equations for gas evolution by taking the dynamic steady state, a generalization of the Oriani equilibrium for multiple isotopes and multi-occupancy traps. The gas diffusivity varies most with mobile fraction when the total gas concentration approximates the trap density. We show HI binding to a monovacancy in vanadium produces a nonmonotonic dependence between diffusivity and gas concentration, unlike the tungsten system. We demonstrate the difference between multiple single occupancy traps and multi-occupancy traps in long-term diffusion dynamics. The applicability of the multi-occupancy, multi-isotope model in steady state is assessed by comparison to an isotope exchange experiment between hydrogen and deuterium in self-ion irradiated tungsten. The vacancy distribution is estimated with molecular dynamics, and the retention across sample depth shows good agreement with experiment using no fitting parameters.