Magnetic properties of CrFeCoNi based high entory alloy

Monte Carlo simulations are performed on three high entropy alloys: Cr0.25Fe0.25Co0.25Ni0.25, Cr0.2Fe0.2Co0.2Ni0.2Pd0.2, and Cr0.2Mn0.2Fe0.2Co0.2Ni0.2, with exchange interactions extracted from The ab initio Korringa-Kohn-Rostoker method combined with the coherent potential approximation calculations. Using finite size scaling analyses, we estimate the magnetic phase transition temperature for the four component alloy to be 108(2) K, and although the individual critical exponents are different from 3D Heisenberg universality class, the reduced exponent follows Suzuki weak universality. With the additional Palladium component, the transition temperature elevates to about 200 K. In contrast, we find no magnetic order for the five component alloy with Manganese at any finite temperatures.

An ab initio investigation of the electronic and magnetic properties of graphite and nickel-doped graphite

In this paper, the KKR (Korringa, Kohn, and Rostoker) is presented with coherent potential approximation methods which is used to investigate the electronic and magnetic properties of allotropic graphite forms of carbon and nickel-doped graphite. The density of states (DOS), band structure, total energy, and the magnetic moments of atoms are computed. The crystallographic structure optimization is carried out by evaluating the total energy as a function of unit lattice parameters. The DOS analysis reveals a partially metallic behavior of the compound. The magnetism vs the Ni-doping content in C1−xNix is also investigated by computing moments induced on atoms; the sensitivity of the magnetism to Ni-doping is also analyzed.

Ab initio calculations of conduction band effective mass parameters of thermoelectric $${\hbox {Mg}}_{2} {\hbox {X}}_{1{-}x} {\hbox {Y}}_x$$ (X, Y = Si, Ge, Sn) alloys

Since there are still research interests in the physical properties of quasi-binary thermoelectric $${\hbox {Mg}}_{2} {\hbox {X}}_{1-x}{\hbox {Y}}_{x}$$ Mg 2 X 1 - x Y x alloys, with X, Y = Si, Ge, Sn, we present an ab initio analysis that yields the relative formation energy and effective masses of the conduction bands, in the whole compositional range x. We base our calculations on the full-relativistic Korringa, Kohn and Rostocker (KKR) Green’s functions formalism within the coherent potential approximation (CPA). Formation energies, measured relative to the end $${\hbox {Mg}}_{2} \hbox {X}$$ Mg 2 X compounds, show no excess energy for the $${\hbox {Mg}}_{2} \hbox {Si} {-} {\hbox {Mg}}_{2} \hbox {Ge}$$ Mg 2 Si - Mg 2 Ge substitution thus indicating a complete solubility. In contrast, concave and asymmetric formation energies for intermediate compositions in the $${\hbox {Mg}}_{2} \hbox {X} {-} {\hbox {Mg}}_{2} \hbox {Sn}$$ Mg 2 X - Mg 2 Sn alloys manifest a miscibility gap. With this basis, we compute and discuss the crossing of the conduction bands observed in n-type $${\hbox {Mg}}_{2} {\hbox {X}}_{1-x} {\hbox {Sn}}_x$$ Mg 2 X 1 - x Sn x materials. We present direction- and band-dependent effective masses using a generalized single parabolic band effective mass approximation to discuss anisotropic effects, to interpret available experimental and theoretical data, and to predict intermediate and not yet published transport parameters on these alloys.

Mechanical properties of CrFeCoNiCux (0 ≤ x ≤ 0.3) HEAs from first-principles calculations

Frist-principles calculations combined with exact muffin-tin orbitals and coherent potential approximation methods is conducted to investigate the effects of Cu content on mechanical properties of CrFeCoNiCux (0 ≤ x ≤ 0.3) HEAs.

Рассеяние электронов и дырок глубокими примесями в полупроводниковых гетероструктурах с квантовыми ямами

Electron and hole scattering by deep impurities in gallium arsenide heterostructures with two quantum wells under arbitrary doping profile was considered within the strongly localized potential approximation. The de-pendence of scattering rate on the carrier energy was shown to reproduce the step-like form of the density of states for size quantization subbands of the heterostructure accounting for the contribution of the overlap integral of the carrier wave functions. For hole subbands of negative effective mass the scattering rates at the subband edges have singularities common for one-dimensional systems.

The Spin-Disorder Resistivity: The Disordered Local Moment Approach

The spin-disorder resistivity (SDR) of a broad range of magneticmaterials, both ordered and disordered, is reviewed.We identify the SDR at the critical temperature with the residualresistivity of the corresponding system evaluated in the frameworkof the disordered local moment (DLM) model.The underlying electronic structure is determined in the frameworkof the tight-binding linear muffin-tin orbital method which employsthe coherent potential approximation to describe the DLM stateand chemical disorder.The DLM fixed-spin moment method is used in the case when the DLMmoment collapses.The Kubo-Greenwood approach is employed to estimate the resistivityof the DLM state.Formalism is applied to Fe and Ni and its alloys, Heusler alloys,and ordered ferromagnetic and antiferromagnetic alloys.Finally, the SDR of the Earth's core will be studied using thesame formalism.Calculations are compared with available experimental data.