We present an Atom-Pair Bond (APB) theory for the energy of a metallic bond based on the ideas of covalent bonding proposed by Pauling. An expression is derived which accurately predicts the signs of the heats of formation of binary alloys. It also explains the characteristics of the Rajasekharan-Girgis lines and their ability to predict accurately concomitant and mutually exclusive structure types in phase diagrams. Evidence is provided to show that the charge transfer on the atom-pair bond which is central to the present theory decides the experimentally observed volume changes on alloying.
First principles studies were performed in order to find out the possibility of inducing half-metallicity in Heusler Compound CoFeMnSb, by means of alloying it with 3d-transition metal elements. Proper alloying element is selected through the calculations of formation energies. These calculations were tested with different concentrations of alloying elements at different atomic sites. Among the selected transition metal elements Sc and Ti are proposed to be excellent alloying elements particularly at Mn site. By using these alloying elements complete half metallic behaviour is obtained in CoFe…
The realization of air-stable 2D metals epitaxial to SiC and capped by graphene creates a potentially immense chemical space of 2D metals and alloys that could expand the variety of solid-state excitations unique to 2D metals beyond what is known for graphene and niobium/tantalum chalcogenides. We perform a high-throughput computational survey from first-principles predicting the structures and stabilities of all metals in the periodic table when they intercalate graphene/SiC. Our results not only agrees with all experimentally known metal/SiC structures explored so far, but also reveals consp…
It has been known that even though two elemental metals, $X$ and $Y$, are immiscible, they can form alloys on surfaces of other metal $Z$. In order to understand such surface alloying of immiscible metals, we study the energetic stability of binary alloys, $XZ$ and $YZ$, in several structures with various coordination numbers (CNs). By analyzing the formation energy modified to enhance the subtle energy difference between metastable structures, we find that $XZ$ and $YZ$ with B2-type structure (CN$=$8) become energetically stable when the $X$ and $Y$ metals form an alloy on the $Z$ metal surfa…
Research on two-dimensional (2D) topological insulators (TIs) is obstructed due to the lack of feasible approaches to growing 2D TIs in experiments. Through systematic first-principles calculations and tight-binding simulations, we propose that alloying Os in 2D MoX2 (X = S, Se, Te) monolayers is an effective approach to inducing semiconductor-to-TI transitions, with sizable nontrivial gaps of 25-37 meV. Analysis of the electronic structures reveals that the topological property mainly originates from the 5d orbitals of the Os atom. Furthermore, the TI gaps can be modulated by external biaxial…
Multicomponent alloying has displayed extraordinary potential for producing exceptional structural and functional materials. However, the synthesis of single-phase, multi-principal covalent compounds remains a challenge. Here we present a diffusion-controlled alloying strategy for the successful realization of covalent multi-principal transition metal carbides (MPTMCs) with a single face-centered cubic (FCC) phase. The increased interfacial diffusion promoted by the addition of a nonstoichiometric compound leads to rapid formation of the new single phase at much lower sintering temperature. Di…
Minor alloying is widely used to control mechanical properties of metallic glasses (MGs). The present understanding of how a small amount of alloying element changes strength is that the additions lead to more efficient packing of atoms and increased local topological order, which then increases the barrier for shear transformations and the resistance to plastic deformation. Here, we discover that minor alloying can improve the strength of MGs by increasing the chemical bond strength alone and show that this strengthening is distinct from changes in topological order. The results were obtained…
Tunable magnetization damping in transition metal ternary alloys
我们表明，坡莫合金，Ni 80 Fe 20（"Py“），磁化阻尼，可以充分提高，以减少后切换磁化旋进到一个可接受的水平，通过与过渡金属锇（Os）合金化。阻尼单调增加后，提高的Os-浓度在Py，至少高达9%的Os。其他的影响与Os合金化的抑制磁化和增强面内各向异性。在与本研究中包括的五种其他过渡金属（4d元素：Nb、Ru、Rh; 5d元素：Ta、Pt）合金化后，磁化阻尼也显著增加，但从未像与Os合金化那样强烈。
Aluminum nitride (AlN) is an important piezoelectric material for a wide range of applications, many efforts are devoted to improving its piezoelectric response by alloying with transition metals (TMs). In this paper, the influence of the type and distribution of TM on the piezoelectric response is discussed for the first time. TM0.0625Al0.9375N with twenty-eight different TMs are investigated, and most show higher values of piezoelectric strain modulus d33 than that of AlN. This is because the TM introduces weaker TM-N bonds and locates closer to the centre of three neighbouring N atoms. The …
Activating Basal Planes in Transition Metal Dichalcogenides for CO2 Reduction to CO through Alloying
Institute of Materials Science & Engineering, Washington University in St. Louis（华盛顿大学圣路易斯分校材料科学与工程研究所）；Department of Computer Science & Engineering, Washington University in St. Louis（华盛顿大学圣路易斯分校计算机科学与工程系）；Department of Mechanical Engineering & Materials Science, Washington University in St. Louis（华盛顿大学圣路易斯分校机械工程与材料科学系）；Department of Chemistry, Incheon National University（仁川国立大学化学系）
In this work we introduce a metal-oxide bond-energy model for alloy oxides based on pure-phase bond energies and bond synergy factors that describe the effect of alloying on the bond energy between cations and oxygen, an important quantity to understand formation and stability of passive films. This model is parameterized for binary cation-alloy oxides using density-functional theory energies and is shown to be directly transferable to multi-component alloy oxides. We parameterized the model for alloy oxide energies with metal cations that form the basis of corrosion resistant alloys, includin…
Surface adsorption, which is often coupled with surface dissolution, is generally unpredictable on alloys due to the complicated alloying and dissolution effects. Herein, we introduce the electronic gradient and cohesive properties of surface sites to characterize the effects of alloying and dissolution. This enables us to build a predictive model for the quantitative determination of the adsorption energy in dissolution, which holds well for transition metals, near-surface alloys, binary alloys, and high-entropy alloys. Furthermore, this model uncovers a synergistic mechanism between the d-ba…
Photocatalytic $H_2$ evolution reactions on pristine TiO$_2$ is characterized by low efficiencies due to trapping and recombination of charge carriers, and due to a sluggish kinetics of electron transfer. Noble metal (mainly Pt, Pd, Au) nanoparticles are typically decorated as cocatalyst on the TiO$_2$ surface to reach reasonable photocatalytic yields. However, owing to the high cost of noble metals, alternative metal cocatalysts are being developed. Here we introduce an approach to fabricate an efficient noble metal free photocatalytic platform for $H_2$ evolution based on alloyed NiCu cocata…
Spin-orbit torque manifested as an accumulated spin-polarized moment at nonmagnetic normal metal, and ferromagnet interfaces is a promising magnetization switching mechanism for spintronic devices. To fully exploit this in practice, materials with a high spin Hall angle, i.e., a charge-to-spin conversion efficiency, are indispensable. To date, very few approaches have been made to devise new nonmagnetic metal alloys. Moreover, new materials need to be compatible with semiconductor processing. Here we introduce W-Ta and W-V alloys and deploy them at the interface between $β$-W/CoFeB layers. Fir…
Employing density functional theory calculations we explore initial stage of competitive alloying of co-deposited silver and indium atoms into a silicon surface. Particularly, we identify respective adsorption positions and activation barriers governing their diffusion on the dimer-reconstructed silicon surface. Further, we develop a growth model that properly describes diffusion mechanisms and silicon morphology with the account of silicon dimerization and the presence of C-type defects. Based on the surface kinetic Monte Carlo simulations we examine dynamics of bimetallic adsorption and elab…
While solid-state materials are commonly classified as covalent, ionic, or metallic, there are cases that defy these iconic bonding mechanisms. A prominent example is given by phase-change materials (PCMs) for data storage or photonics, which have recently been argued to show 'resonant' bonding; a clear definition of this mechanism, however, has been lacking until the present day. Here we show that these solids are clearly different from resonant bonding in the pi-orbital systems of benzene and graphene. Instead, they exhibit a unique mechanism between covalent and metallic bonding, which we c…
In our recent works, we used a nearest-neighbor broken bond (NNBB) model to fit the surface energy of Pt, Pd, and Au surfaces [Adv. Theory Simul. 1800127 (2018)]. It was verified that this model could describe the surface energies of above noble metals with high accuracy. The applications of this model in real-time simulations of equilibrium nanocrystal transformations are in good agreements with the experimental observations at macroscopic time scales quantitatively. In this work, we want to further verify the generality of the NNBB model for other transition metals. All surface tentions and …
Explicit treatment of hydrogen bonds in the Universal Force Field: validation and application for Metal-Organic Frameworks, hydrates and host-guest complexes
Rate-Dependent Reversibility and Lithium Losses in Hybrid Anode-Collector Metal Electrodes
Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid（马德里自治大学凝聚态物理系）；Instituto Universitario de Ciencia de Materiales Nicolás Cabrera (INC), Universidad Autónoma de Madrid（马德里自治大学尼古拉斯·卡布雷拉材料科学大学研究所）；Centro de Micro-Análisis de Materiales (CMAM), Universidad Autónoma de Madrid（马德里自治大学材料微分析中心）；Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid（马德里自治大学凝聚态物理中心）
We investigated the bond, electronic and magnetic behavior of adsorption Yttrium atoms on Lithium (110) surface using a combination of Bond-order-length-strength(BOLS) correlation and density-functional theory(DFT). We found that adsorption Y atoms on Li(110) surfaces form two-dimensional (2D) geometric structures of hexagon, nonagon, solid hexagonal, quadrangle and triangle. The consistent with the magnetic moment are 6.66μB, 5.54μB, 0.28μB, 1.04μB, 2.81μB, respectively. In addition, this work could pave the way for design new 2D metals electronic and magnetic properties.
Electronic Structure, mass fluctuation, and Localized Bond Properties of two-dimensional double-layer transition metal chalcogenide MX$_2$ (M = Mo, W; X = S, Se, Te) Calculated Based on Density Functional Theory and BBC model
The hybrid perovskites are coordination frameworks with the same topology as the inorganic perovskites, but with properties driven by different chemistry, including host-framework hydrogen bonding. Like the inorganic perovskites, these materials exhibit many different phases, including structures with potentially exploitable functionality. However, far less is known about their behaviour under pressure. We have studied the structures of of manganese and cobalt guanidinium formate under pressure using single-crystal X-ray and powder neutron diffraction. Remarkably, when pressure reduces these m…
Bond pads are the electrical interconnections of a microelectronic device to the outside world. A polyimide layer (PI) on top of a microelectronic device protects the whole device against environmental impacts. The bond pads are accessible though openings in this electrically insulating layer. The oxide layer thickness and contaminations at the Al bond pad surface influence as well the quality of the mechanical and electrical joint between bond pad and bond wire as the durability of this interconnection. If a bond pad surface has to be analyzed with high spatial resolution Auger electron spect…
Some ABX3 perovskites exhibit different local environments (DLE) for the same B atoms in the lattice, an effect referred to as disproportionation, distinguishing such compounds from perovskites that have single local environments (SLE). The basic phenomenology of disproportionation involves the absence of B-atom charge ordering, the creation of different B-X bond length for different local environments, the appearance of metal (in SLE) to insulator (in DLE) transition, and the formation of ligand holes. We point out that this phenomenology is common to a broad range of chemical bonding pattern…
Aiming towards materials design for methane activation, we study temperature ($T$), pressure ($p$) dependence of the composition, structure, and stability of metal oxide clusters in a reactive atmosphere using a prototypical model catalyst having wide applications: free transition metal (Ni) clusters in a combined oxygen and methane atmosphere. A robust methodological approach is employed, to show that the conventional harmonic approximation miserably fails for this class of materials and capturing anharmonic effects to the vibration free energy contribution is indispensable. To incorporate th…
We investigated the mechanism of Na/Ta(110) and Ta/Na(110) interfaces using a combination of bond band barrier (BBB) and zone selective electron spectroscopy (ZES) correlation. We found that 7/9 ML and 8/9 ML Ta metal on a Na(110) surface form one dimensional (1D) chain and two dimensional (2D) ring structures, respectively. Moreover, we show that on Na(110), the Ta-induced Na(110) surface binding energy (BE) shifts are dominated by quantum entrapment. On the contrary, on a Ta(110) surface, the Na-induced Ta(110) surface BE shifts are dominated by polarization. Thus, the BBB and ZES strategy c…
