Evaluation of thermodynamics, formation energetics and electronic properties of vacancy defects in CaZrO3

Using first-principles total energy calculations we have evaluated the thermodynamics and the electronic properties of intrinsic vacancy defects in orthorhombic CaZrO3. Charge density calculations and the atoms-in-molecules concept are used to elucidate the changes in electronic properties of CaZrO3 upon the introduction of vacancy defects. We explore the chemical stability and defect formation energies of charge-neutral as well as of charged intrinsic vacancies under various synthesis conditions and also present full and partial Schottky reaction energies. The calculated electronic properties indicate that hole-doped state can be achieved in charge neutral Ca vacancy containing CaZrO3 under oxidation condition, while reduction condition allows to control the electrical conductivity of CaZrO3 depending on the charge state and concentration of oxygen vacancies. The clustering of neutral oxygen vacancies in CaZrO3 is examined as well. This provides useful information for tailoring the electronic properties of this material. We show that intentional incorporation of various forms of intrinsic vacancy defects in CaZrO3 allows to considerably modify its electronic properties, making this material suitable for a wide range of applications

Quasi Three-Dimensional Tetragonal SiC Polymorphs as Efficient Anodes for Sodium-Ion Batteries

In the present work, we investigate, for the first time, quasi 3D porous tetragonal silicon–carbon polymorphs t(SiC)12 and t(SiC)20 on the basis of first-principles density functional theory calculations. The structural design of these q3-t(SiC)12 and q3-t(SiC)20 polymorphs follows an intuitive rational approach based on armchair nanotubes of a tetragonal SiC monolayer where C–C and Si–Si bonds are arranged in a paired configuration for retaining a 1:1 ratio of the two elements. Our calculations uncover that q3-t(SiC)12 and q3-t(SiC)20 polymorphs are thermally, dynamically, and mechanically stable with this lattice framework. The results demonstrate that the smaller polymorph q3-t(SiC)12 shows a small band gap (∼0.59 eV), while the larger polymorph of q3-t(SiC)20 displays a Dirac nodal line semimetal. Moreover, the 1D channels are favorable for accommodating Na ions with excellent (&gt;300 mAh g–1) reversible theoretical capacities. Thus confirming potential suitability of the two porous polymorphs with an appropriate average voltage and vanishingly small volume change (&lt;6%) as anodes for Na-ion batteries.Validerad;2023;Nivå 2;2023-11-13 (hanlid);Full text license: CC BY</p

Elucidating the Surface Properties of Sr₃PbO Inverse-Perovskite Topological Insulator: A First-Principles Study

The emergence of robust surface electronic states in topological insulators such as bulk Sr3PbO inverse-perovskite makes them suitable candidates for spintronic devices and solid-state quantum computers. Herein, the atomic structure, surface energetics, and electronic properties of Sr3PbO inverse-perovskite Sr2O (SO)-terminated and SrPb-terminated (001) surfaces are examined using density functional theory. A comparison of the computed structural properties of SO-termianted and SrPb-terminated (001) surfaces reveals maximum surface rumpling and changes in interlayer distances for the SrPb-terminated surface of Sr3PbO. However, the calculated surface energies indicate that both SO-termianted and SrPb-terminated (001) surfaces of Sr3PbO are energetically feasible, indicating that these surfaces can coexist in a polycrystalline sample of this material. Due to the presence of Pb in Sr3PbO, a comprehensive examination of the electronic structure of bulk and supercell slab structures of Sr3PbO by taking spin–orbit coupling effects into consideration is conducted. Noninsulating nature of electronic structure for the two possible (001) terminations of Sr3PbO is found. The domination of Pb-6p states at the Fermi energy and the hole screening observed at the SrPb-terminated surface of Sr3PbO support the p-type nature observed in the experiment.</p

Structure inversion asymmetry enhanced electronic structure and electrical transport in 2D A3SnO (A = Ca, Sr, and Ba) anti-perovskite monolayers

Anti-perovskites A3SnO (A = Ca, Sr, and Ba) are an important class of materials due to the emergence of Dirac cones and tiny mass gaps in their band structures originating from an intricate interplay of crystal symmetry, spin-orbit coupling, and band overlap. This provides an exciting playground for modulating their electronic properties in the two-dimensional (2D) limit. Herein, we employ first-principles density functional theory (DFT) calculations by combining dispersion-corrected SCAN + rVV10 and mBJ functionals for a comprehensive side-by-side comparison of the structural, thermodynamic, dynamical, mechanical, electronic, and thermoelectric properties of bulk and monolayer (one unit cell thick) A3SnO anti-perovskites. Our results show that 2D monolayers derived from bulk A3SnO anti-perovskites are structurally and energetically stable. Moreover, Rashba-type splitting in the electronic structure of Ca3SnO and Sr3SnO monolayers is observed owing to strong spin-orbit coupling and inversion asymmetry. On the other hand, monolayer Ba3SnO exhibits Dirac cone at the high-symmetry Γ point due to the domination of band overlap. Based on the predicted electronic transport properties, it is shown that inversion asymmetry plays an essential character such that the monolayers Ca3SnO and Sr3SnO outperform thermoelectric performance of their bulk counterparts.Validerad;2023;Nivå 2;2023-04-20 (hanlid)</p