Chemical Bonding in Metallic Glasses from Machine Learning and Crystal Orbital Hamilton Population
Ary R. Ferreira
备注：
This update contains a number of enhancements. The manuscript has been updated after an anonymous review process by a journal whose policies discourage posting material from this process online. Few changes have been done in Sections I, II and III-A; however, Section III-B and IV have undergone significant changes
The chemistry (composition and bonding information) of metallic glasses (MGs) is at least as important as structural topology for understanding their properties and production/processing peculiarities. This article reports a machine learning (ML)-based approach that brings an unprecedented "big picture" view of chemical bond strengths in MGs of a prototypical alloy system. The connection between electronic structure and chemical bonding is given by crystal orbital Hamilton population (COHP) analysis; within the framework of density functional theory (DFT). The stated comprehensive overview is made possible through a combination of: efficient quantitative estimate of bond strengths supplied by COHP analysis; representative statistics regarding structure in terms of atomic configurations achieved with classical molecular dynamics simulations; and the smooth overlap of atomic positions (SOAP) descriptor. The study is supplemented by an application of that ML model under the scope of mechanical loading; in which the resulting overview of chemical bond strengths revealed a chemical/structural heterogeneity that is in line with the tendency to bond exchange verified for atomic local environments. The encouraging results pave the way towards alternative approaches applicable in plenty of other contexts in which atom categorization (from the perspective of chemical bonds) plays a key role.
A structural study is presented of ab-initio molecular dynamics simulations of Ge-As-Se calcogenide glasses performed at the same mean coordination number but differing stoichiometry ranging between Se rich and Se poor glasses. Starting configurations are generated via Reverse Monte Carlo (RMC) simulations of Extended X-ray Absorption Fine Structure (EXAFS) measurements of experimental samples. Structural analysis is presented illustrating the bonding trends found with changing stoichiometry.
The structure of $\mathrm{Ge}_x\mathrm{Te}_{100-x}$ (x = 14.5, 18.7, 23.6) glasses prepared by twin roller quenching technique was investigated by neutron diffraction, X-ray diffraction and Ge-K-edge X-ray absorption spectroscopy measurements. Large scale structural models were obtained for each composition by fitting the experimental datasets in the framework of the reverse Monte Carlo technique. It was found that the majority of Ge and Te atoms satisfy the 8-N rule. Simulation results indicate that Ge-Ge bonding is not significant for x = 14.5 and 18.7. The shape and position of the first pe…
Chemical design of SiO2-based glasses with high elastic moduli and low weight is of great interest. However, it is difficult to find a universal expression to predict the elastic moduli according to the glass composition before synthesis since the elastic moduli are a complex function of interatomic bonds and their ordering at different length scales. Here we show that the densities and elastic moduli of SiO2-based glasses can be efficiently predicted by machine learning (ML) techniques across a complex compositional space with multiple (>10) types of additive oxides besides SiO2. Our machine …
We use \textit{ab initio} molecular dynamics simulations to investigate the properties of the dry surface of pure silica and sodium silicate glasses. The surface layers are defined based on the atomic distributions along the direction ($z-$direction) perpendicular to the surfaces. We show that these surfaces have a higher concentration of dangling bonds as well as two-membered (2M) rings than the bulk samples. Increasing concentration of Na$_2$O reduces the proportion of structural defects. From the vibrational density of states, one concludes that 2M rings have a unique vibrational signature …
The atomic structure, electronic structure and physical properties of $(TiZrNbCu)_{(1-x)}Ni_x$ (x $\leq$ 0.5) metallic glasses (MG) were studied in both the high-entropy (0<x<0.35) and the higher Ni concentration range (x $\geq$ 0.35). Atomic structure studies performed with X-ray diffraction and synchrotron powder diffraction provided average atomic volumes, structure factors, radial distribution functions, coordination numbers and packing densities. Electronic structure studies performed using photoemission spectroscopy and low-temperature specific heat provided information about the electro…
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…
We formulate Wannier orbital overlap population and Wannier orbital Hamilton population to describe the contribution of different orbitals to electron distribution and their interactions. These methods, which are analogous to the well known crystal orbital overlap population and crystal orbital Hamilton population, provide insight into the distribution of electrons at various atom centres and their bonding nature. We apply this formalism in the context of a plane-wave density functional theory calculation. This method provides a means to connect the non-local plane-wave basis to a localised ba…
X-ray photo-induced atomic motion in Phase Change Materials and conventional covalent chalcogenide glasses
Institut Néel, Université Grenoble Alpes and Centre National de la Recherche Scientifique（尼斯研究所，格勒诺布尔阿尔卑斯大学及法国国家科学研究中心）；Department of Physics, University of Trento（特伦托大学物理系）；Department of Chemistry, Aarhus University（奥胡斯大学化学系）；European Synchrotron Radiation Facility（欧洲同步辐射装置）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；ICGM, Université de Montpellier, CNRS, ENSCM（材料化学与全球分子实验室，蒙彼利埃大学，法国国家科学研究中心及国立化学学院）
Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectra (XPS) of Nd doped phosphate glasses have been studied before and after gamma irradiation in order to find the behavior of chemical bonds, which decide the structural changes in the glass samples. IR absorption spectra of these glasses are found dominated mainly by the characteristics phosphate groups, water (OH) present in the glass network as well as on the composition of glass matrix. The effects of gamma irradiation are observed in the form of bond breaking and possible re-arrangement of the bonding in the glass. Ener…
The nuclear waste problem is one of the main interests of the rare earth and actinide elements chemistry. Studies of Actinide-containing compounds are at the frontier of the applications of current theoretical methods due to the need to consider relativistic effects and approximations to the Dirac equation in them. Here, we employ four-component relativistic quantum calculations and scalar approximations to understand the contribution of f-type atomic orbitals in the chemical bonding of actinides (Ac) to organic ligands. We studied the relativistic quantum structure of an isostructural family …
First-Principles Study of Magnetism, Electronic Structure, and Bonding in Nb-Mn-Ge Kagome Compounds
Ames National Laboratory, U.S. Department of Energy, Iowa State University（艾姆斯国家实验室，美国能源部，爱荷华州立大学）；Department of Physics and Astronomy, Iowa State University（爱荷华州立大学物理与天文系）；Department of Physics, Xiamen University（厦门大学物理系）
We present the results of theoretical investigation on the electronic structure, bonding nature and ground state properties of Th$_2$Al and Th$_2$AlH$_4$ using generalized-gradient-corrected first-principles full-potential density-functional calculations. Th$_2$AlH$_4$ has been reported to violate the "2 Årule" of H-H separation in hydrides. From our total energy as well as force-minimization calculations, we found a shortest H-H separation of 1.95 Å in accordance with recent high resolution powder neutron diffraction experiments. When the Th$_2$Al matrix is hydrogenated, the volume expansion …
Accelerating Discovery of Extreme Lattice Thermal Conductivity by Crystal Attention Graph Neural Network (CATGNN) Using Chemical Bonding Intuitive Descriptors
Using the recently developed Nth-order muffin-tin-orbital (NMTO) based downfolding technique we revisit the electronic properties of half-metallic ferromagnets, the semi-Heusler NiMnSb and rutile CrO2. The NMTO Wannier orbitals for the Mn-d and Cr-t2g manifolds are constructed and the mechanism of chemical bonding is discussed. The effective hopping Hamiltonian parameters are calculated using a NMTO downfolded basis set. We propose model Hamiltonian parameters with possibly minimal basis sets for both half-metallic ferromagnetic alloys.
This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor…
The structural optimization and energetics studies of SiC graphitic-like structures have been investigated theoretically in the context of formations of stable graphitic-like layer structures, single- and multi-walled nanotubes using the DFT-based Vienna ab-inito simulation package. The bonding nature of atoms in the optimized structures has been examined using a local analysis technique based on a self-consistent and environment-dependent semi-empirical Hamiltonian. Results of our studies reveal that stabilized SiC graphitic-like layer structures possess the sp2 bonding nature, different from…
We have investigated the effects of the interfacial bond arrangement on the electronic transport features of metal-nanotube-metal systems. The transport properties of finite, defect-free armchair and zigzag single-walled carbon nanotubes attached to Au(111) metallic contacts have been calculated by means of the non-equilibrium Green functional formalism with the Tight-Binding and the Extended Huckel Hamiltonians. Our calculations show that the electrode material is not the only factor which rules contact transparency. Indeed, for the same electrode, but changing nanotube helicities, we have ob…
Semiconductor glasses exhibit many unique optical and electronic anomalies. We have put forth a semi-phenomenological scenario (J. Chem. Phys. 132, 044508 (2010)) in which several of these anomalies arise from deep midgap electronic states residing on high-strain regions intrinsic to the activated transport above the glass transition. Here we demonstrate at the molecular level how this scenario is realized in an important class of semiconductor glasses, namely chalcogen and pnictogen containing alloys. Both the glass itself and the intrinsic electronic midgap states emerge as a result of the f…
An atomic-scale theory of the viscoelastic response of metallic glasses is derived from first principles, using a Zwanzig-Caldeira-Leggett system-bath Hamiltonian as a starting point within the framework of nonaffine linear response to mechanical deformation. This approach provides a Generalized-Langevin-Equation (GLE) as the average equation of motion for an atom or ion in the material, from which non-Markovian nonaffine viscoelastic moduli are extracted. These can be evaluated using the vibrational density of states (DOS) as input, where the boson peak plays a prominent role for the mechanic…
Machine-learned multi-orbital tight-binding (MMTB) Hamiltonian models have been developed to describe the electronic characteristics of intermetallic compounds $\rm Mg_2Si, Mg_2Ge, Mg_2Sn$, and $\rm Mg_2Pb$ subject to strain. The MMTB models incorporate spin-orbital mediated interactions and they are calibrated to the electronic band structures calculated via density functional theory (DFT) by a massively parallelized multi-dimensional Monte-Carlo search algorithm. The results show that a machine-learned five-band tight-binding model reproduces the key aspects of the valence band structures in…
The emergence of scanning probe and electron beam imaging techniques have allowed quantitative studies of atomic structure and minute details of electronic and vibrational structure on the level of individual atomic units. These microscopic descriptors in turn can be associated with the local symmetry breaking phenomena, representing stochastic manifestation of underpinning generative physical model. Here, we explore the reconstruction of exchange integrals in the Hamiltonian for the lattice model with two competing interactions from the observations of the microscopic degrees of freedom and e…
College of Physics, Chengdu University of Technology（成都理工大学物理学院）；Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford（牛津大学化学系物理与理论化学实验室）；Laboratoire Charles Coulomb (L2C), University of Montpellier and CNRS（蒙彼利埃大学与法国国家科学研究中心夏尔·库隆实验室）
