In the quest for novel thermoelectric materials to harvest waste environmental heat, we investigate alkali metal-based Zintl phases X$_2$AgY (X = Na, K, and Y Sb, Bi) utilizing first-principles methods. We obtain significantly low lattice thermal conductivity values ranging 0.9-0.5 W m$^{-1}$ K$^{-1}$ at 300~K, challenging established such as SnSe, PbTe, Bi$_2$Te$_3$ well other phases. trace astonishingly anharmonicity, large phonon scattering phase space, velocities, lifetimes. K-based...

The critical need in novel or alternative approaches to energy production, conversion, and harvesting, combined with the ongoing pursuit of device miniaturization, have revived interest long-known but ``doomed'' impractical caloric effects solids. Contrary old belief that such effects, while common, are miniscule, a large variety giant has been recently discovered some ferroic materials. These discoveries opened door use these an efficient environmentally friendly solid-state refrigeration...

Ferroelectrics and antiferroelectrics appear to have just the opposite behavior upon scaling down. Below a critical thickness of few nanometers ferroelectric phase breaks into nanodomains that mimic electric properties very closely. On other hand, antiferroelectric thin films were found transition from one under certain growth conditions. At present, origin such is controversial. Here, we use accurate first-principles-based finite-temperature simulations predict existence for...

Antiferroelectrics are under extensive reexamination owing to their unique properties and technological promise. Computationally, they pose a challenge for predictive modeling as often do not possess well-defined localized electric moments exhibit delicate energetic balance between polar antipolar phases. We propose first-principles-based atomistic model the prototype antiferroelectric ${\mathrm{PbZrO}}_{3}$ that captures accurately wide range of its properties. Application study...

Zintl phases have excellent thermoelectric prospects to put the waste heat good use. In quest for same, using first-principles methods combined with Boltzmann transport theory, we explored two recent phases, NaSrSb and NaBaSb. We found remarkably low lattice thermal conductivities of 0.7 (2.1) 0.4 (1.4) W m–1 K–1 at 900 K (300 K) NaBaSb, respectively, which are same order as other potential such Sr3AlSb3 BaCuSb. find that values could be attributed short phonon lifetimes small group...

Ferroelectric PbTiO${}_{3}$ occupies a special place among ferroelectric materials owing to its unique status as prototype displacive ferroelectric. However, while undoubtedly provides one of the best examples phase transitions, several experimental and theoretical findings seem suggest certain degree order-disorder mechanism associated with transition. While multiple efforts have been undertaken better understand nature transition in this classic ferroelectric, subject still remains...

Abstract Electrocaloric effect is presently under active investigation owing to both the recent discoveries of giant electrocaloric effects and its potential for solid state cooling applications. We use first-principles-based direct simulations predict temperature change in ferroelectric ultrathin nanowires. Our findings suggest that nanowires with axial polarization direction maximum response reduced when compared bulk, while room properties can be enhanced by tuning transition temperature....

Abstract The ZrSiS-class of layered materials offer interesting topological and magnetic characteristics suitable for spintronics applications. In
this work, we have synthesized a polycrystalline NdBiTe using solid-state reaction technique examined the properties in 2 - 300 K temperature range field-dependent magnetization measurements. Our specific heat
data demonstrates long-range antiferromagnetic ordering material below 4.5 K. Furthermore, our isothermal data
show...

High entropy perovskite oxides have the potential to significantly enhance electrode performance in solid oxide fuel cells (SOFCs) and batteries. However, not all high configurations yield single-phase oxides....

Partial charge compensation in ferroelectric nanostructures is known to play a critical role stabilizing equilibrium domain patterns. We use first-principles-based simulations study the effect of partial on response polarization electric field PbTiO3 and BaTiO3 ultrathin films. Computational data predict that can be altered at qualitative level by tailoring compensation. report an unusual transition from antiferroelectric dielectric behavior induced change amount compensating charge....

We demonstrate an iterative scheme for coupled-cluster properties calculations without truncating the dressed operator. For validation, magnetic dipole hyperfine constants of alkaline Earth ions are calculated with relativistic and role electron correlation examined. Then, a detailed analysis higher order terms is carried out. Based on results, we arrive at optimal form Which recommend theory.

The perturbed relativistic coupled-cluster (PRCC) theory is applied to calculate the electric dipole polarizabilities of alkaline Earth metal atoms. Dirac-Coulomb-Breit atomic Hamiltonian used and we include triple excitations in (RCC) theory. theoretical issues related excitation cluster operators are described detail also provide details on computational implementation. PRCC results good agreement with experimental previous results. We, then, highlight importance considering Breit interaction for

The main roadblock on the way to practical realization of magnetoelectric devices is lack multiferroics with strong coupling. We propose an unusual route dramatically enhance this coupling through a thermally mediated mechanism. Such effect quantified by isentropic rather than isothermal response and computed here from first principles. A robust enhancement predicted for both naturally occurring heterostructured materials.

Abstract A combination of theoretical and first-principles computational methods, along with experimental evidence from the literature, were used to predict existence a scaling law for electrocaloric temperature change in antiferroelectric materials. We show that scales quadratically electric field, allowing simple transformation collapse set Δ T ( E ) onto single curve. This offers unique method can be behavior beyond limits present measurement ranges or regions where data are not yet available.

We have carried out a detailed and systematic study of the correlation energies inert gas atoms Ne, Ar, Kr, Xe using relativistic many-body perturbation theory coupled-cluster theory. In calculations, we implement perturbative triples include these in energy calculations. then calculate dipole polarizability ground states perturbed

We have developed an all particle Fock-space relativistic coupled-cluster method for two-valence atomic systems. then describe a scheme to employ the wave function calculate properties. Based on these developments we excitation energies, magnetic hyperfine constants and electric dipole matrix elements of Sr, Ba Yb. Further more, quadrupole HFS Sr$^+$, Ba$^+$ Yb$^+$. For use one-valence functions obtained as intermediate in calculations. also

Abstract This article presents spectroscopy results of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>5</mml:mn> <mml:mi>s</mml:mi> <mml:mi>p</mml:mi> <mml:msup> <mml:mstyle scriptlevel="0"/> <mml:mn>3</mml:mn> </mml:msup> </mml:mrow> <mml:msub> <mml:mi>P</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo stretchy="false">→</mml:mo> <mml:mi>d</mml:mi> <mml:mi>D</mml:mi> <mml:mn>1</mml:mn> </mml:math> transition in all isotopes laser cooled Sr...

We use perturbed relativistic coupled-cluster (PRCC) theory to calculate the electric dipole polarizability of noble-gas atoms Ar, Kr, Xe, and Rn. also provide a detailed description nonlinear terms in PRCC consider Dirac-Coulomb-Breit atomic Hamiltonian for calculations. find that largest contribution from Breit interaction is 0.1$%$, case As we go Ar Rn, based on pattern random-phase-approximation effects, contraction outermost ${p}_{1/2}$ orbitals due corrections discernible without any ambiguity.

We use the perturbed relativistic coupled-cluster (PRCC) theory to compute electric dipole polarizabilities $\ensuremath{\alpha}$ of Zn, Cd, and Hg. The computations are done using Dirac-Coulomb-Breit Hamiltonian with Uehling potential incorporate vacuum polarization corrections. To assimilate self-energy corrections we model operator Shabaev et al. [Phys. Rev. A 88, 012513 (2013)]. triple excitations included perturbatively in PRCC nonperturbatively unperturbed sector. Our results for all...

First-principles-based finite-temperature simulations are used to predict the emergence of ferroelectricity in antiferroelectric nanostructures made PbZrO3. The phenomenon is expected occur nanodots, nanowires, and thin films with good surface charge compensation can be explained by recently proposed effect [1]. Our computations provide a microscopic insight into equilibrium phases, phase competition, electrical properties PbZrO3 nanostructures. dependence these on boundary conditions...

Double perovskite materials have shown promising applications as an electrode in solid oxide fuel cells and Li-air batteries for oxygen reduction, evolution, transport. However, degradation of the material due to cation migration surface, forming secondary phases, poses existential bottleneck development. Herein, a theoretical approach combining density functional theory molecular dynamics simulations is presented study Ba-cation segregation double NdBaCo2O5+δ. Solutions circumvent at level...

We develop a method based on the relativistic coupled-cluster theory to incorporate perturbative interaction no-pair Dirac-Coulomb atomic Hamiltonian. The is general and suitable any perturbation Hamiltonian in many electron atom or ion. Using this perturbed (PRCC) we calculate electric dipole polarizability, $\alpha$, of Neon. linearized PRCC results are very good agreement with experimental value. However, nonlinear shows larger uncertainty but it consistent observations from earlier works.

abstractA first-principles-based computational approach is developed to study finite-temperature complex dynamics in multiferroics. Application of the technique one most well-known multiferroic, BiFeO3, predicts existence electromagnons that have so far remained elusive for first-principles computations. It demonstrated general form magnetoelectric coupling allowed any may produce an electromagnon antiferromagnetic ferroelectric. This finding could be explained from basic theory resonance....