A simple physical conception explaining the experimentally observed temperature dependence of the local mode frequencies in the ordering metal hydrides is proposed. Calculations are performed for bcc vanadium deuterides. The model can be applied to other physical phenomena which are related to the hydrogen motion in metal lattices.
Hydrogen ordering influence on the proton spin-lattice relaxation time in metal-hydrogen compoun Hydrogen ordering influence on the proton spin-lattice relaxation time in metal-hydrogen compounds
We investigated the magnetic behavior of metal hydrides FeH$_{x}$, CoH$_{x}$ and NiH$_{x}$ for several concentrations of hydrogen ($x$) by using Density Functional Theory calculations. Several structural phases of the metallic host: bcc ($α$), fcc ($γ$), hcp ($\varepsilon$), dhcp ($\varepsilon'$), tetragonal structure for FeH$_{x}$ and $\varepsilon$-$γ$ phases for CoH$_{x}$, were studied. We found that for CoH$_{x}$ and NiH$_{x}$ the magnetic moment ($m$) decreases regardless the concentration $x$. However, for FeH$_{x}$ systems, $m$ increases or decreases depending on the variation in $x$. In…
Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1$_0$ and L1$_2$ orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phase…
Hydrogen (H) induced damage in metals has been a long-standing woe for many industrial applications. One form of such damage is linked to H clustering, for which the atomic origin remains contended, particularly for non-hydride forming metals. In this work, we systematically studied H clustering behavior in bcc metals represented by W, Fe, Mo, and Cr, combining first-principles calculations, atomistic and Monte Carlo simulations. H clustering has been shown to be energetically favorable, and can be strongly facilitated by anisotropic stress field, dominated by the tensile component along one o…
Hydrogen uptake and hydride formation in Al$_x$CoCrFeNi high-entropy alloys: First-principles, universal-potential, and experimental study
Ruhr-Universität Bochum（波鸿鲁尔大学）；Max-Planck-Institut for Sustainable Materials（马克斯·普朗克可持续材料研究所）；University of Stuttgart（斯图加特大学）；Deutsches Elektronen-Synchrotron DESY（德国电子同步辐射中心）；Goethe University Frankfurt（法兰克福歌德大学）；Federal Institute for Materials Research and Testing (BAM)（联邦材料研究与测试研究所）
In this work we present a study of the structural properties of Fe$_{100-x}$ Ga$_x$ grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption spectroscopy) together with real space imaging by means of Transmission Electron Microscopy and surface sensitive $in situ$ Reflected High Energy Electron Diffraction. For substrate temperature $T_s$ below 400 $^o$C we obtain $bcc$ films while, for $x \approx$ 24 and $T_s \geq$ 400$^o$C the nucleation of the $fcc$ phase is observed. For both systems a Ga anticlus…
Emergent B2 chemical orderings in the AlTiVNb and AlTiCrMo refractory high-entropy superalloys studied via first-principles theory and atomistic modelling
结合从头算电子结构理论与原子尺度蒙特卡罗模拟，研究了 AlTiVNb 和 AlTiCrMo 难熔高熵高温合金的相稳定性，揭示了高温下由 Al 和 Ti 驱动的 B2 化学有序及其对电子结构和电阻率的影响。
Usually the ions of a particular element in solids are in positive or negative oxidation states, depending upon the chemical environment. It is highly unusual for an atom having both positive as well as negative oxidation states simultaneously within the same structural framework in a particular compound. Our structural and chemical bonding analyses show that the hydrogen ions in the transition metal ammine borohydrides (TMABHs) with the chemical formula M(BH4)2(NH3)2 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) have both positive and negative oxidation states. Our detailed analyses confirm …
The effect of grain boundaries on magnetic exchange interactions in iron
Brno University of Technology（布尔诺理工大学）；AGH University of Krakow（克拉科夫AGH科技大学）；Central European Institute of Technology (CEITEC)（中欧技术研究所）；Normandie Université, UNIROUEN, INSA Rouen, CNRS, GPM（诺曼底大学，鲁昂大学，鲁昂国立应用科学学院，法国国家科学研究中心，GPM实验室）
