D. A. Drabold

D. A. Drabold
Ohio University · Department of Physics and Astronomy

Ph.D.

About

359
Publications
40,142
Reads
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8,506
Citations
Introduction
Theory of amorphous materials, electronic structure and methodological development of simulation of materials.
Additional affiliations
August 2008 - August 2009
Trinity College
Position
  • Visiting Fellow Commoner
August 2008 - August 2009
University of Cambridge
Position
  • Leverhulme Professsor
August 2008 - August 2009
Clare Hall, Cambridge
Position
  • Life Fellow
Education
September 1983 - January 1989

Publications

Publications (359)
Article
Full-text available
The general and practical inversion of diffraction data–producing a computer model correctly representing the material explored–is an important unsolved problem for disordered materials. Such modeling should proceed by using our full knowledge base, both from experiment and theory. In this paper, we describe a robust method to jointly exploit the p...
Article
Full-text available
The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using curren...
Article
Full-text available
Materials with optimized band gap are needed in many specialized applications. In this work, we demonstrate that Hellmann-Feynman forces associated with the gap states can be used to find atomic coordinates with a desired electronic density of states. Using tight-binding models, we show that this approach can be used to arrive at electronically des...
Article
Full-text available
We introduce a structural modeling technique, called force-enhanced atomic refinement (FEAR). The technique incorporates interatomic forces in reverse Monte Carlo (RMC) simulations for structural refinement by fitting experimental diffraction data using the conventional RMC algorithm, and minimizes the total energy and forces from an interatomic po...
Article
Full-text available
We apply a method called “force-enhanced atomic refinement” (FEAR) to create a computer model of amorphous silicon (a-Si) based upon the highly precise x-ray diffraction experiments of Laaziri et al. [Phys. Rev. Lett. 82, 3460 (1999)]. The logic underlying our calculation is to estimate the structure of a real sample a-Si using experimental data an...
Preprint
Full-text available
This paper focuses on the structural, electronic, and vibrational features of amorphous graphite [R. Thapa $\textit{et. al.}$, Phys. Rev. Lett. 128, 236402 (2022)]. The structure order in amorphous graphite is discussed and compared with graphite and amorphous carbon. The electronic density of states and localization in these phases were analyzed....
Preprint
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Multi-shell fullerenes "buckyonions" were simulated, starting from initially random configurations, using a density-functional-theory (DFT)-trained machine-learning carbon potential within the Gaussian Approximation Potential (ML-GAP) Framework [Volker L. Deringer and Gabor Csanyi, Phys. Rev. B 95, 094203 (2017)]. A large set of such fullerenes wer...
Preprint
Full-text available
An amorphous graphite material has been predicted from molecular dynamics simulation using ab initio methods. Carbon materials reveal a strong proclivity to convert into a sp2 network and then layer at temperatures near 3000 K within a density range of ca. 2.2 – 2.8 g / cm 3 . Each layer of amorphous graphite is a monolayer of amorphous graphene i...
Chapter
In this chapter, we describe the rationale, need, and character of ab initio simulation with a brief history and some examples. We also describe modeling schemes for amorphous materials, including the melt‐quench method – the simulated slow quenching of an equilibrated liquid. We discuss ab initio structural inversion, the method of “Force Enhanced...
Article
The Special Issue “Form and Function of Disorder” has been assembled to honor David A. Drabold on the occasion of his 60th birthday (see the Guest Editorial, article number 2100366). The issue includes an array of topics on disordered materials encompassing applications of classical, quantum‐mechanical, and machine‐learning approaches to glasses, a...
Article
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Atomistic simulations of (Na2O)x(SiO2)1−x glasses are carried out using the building-block method that uses copies of low-energy units, “building blocks,” to build large realistic structural models. The calculated pair-correlation functions show that the local structure of these glasses is in good agreement with diffraction experiments. The electro...
Article
Full-text available
Structurally disordered materials pose fundamental questions1,2,3,4, including how different disordered phases (‘polyamorphs’) can coexist and transform from one phase to another5,6,7,8,9. Amorphous silicon has been extensively studied; it forms a fourfold-coordinated, covalent network at ambient conditions and much-higher-coordinated, metallic pha...
Article
Herein, the structure of Cu46Zr46Al8 is inverted from X‐ray structure factor data and energy minimizations as implemented with forced enhanced atomic refinement (FEAR). The models generated are in good agreement with structural data obtained from diffraction experiment. Voronoi tessellation analysis shows reasonable agreement with previous results,...
Article
Herein, the Kubo–Greenwood formula is utilized to project the electronic conductivity into real space, and a Hermitian positive semidefinite matrix Γ is discussed, which is called the conduction matrix, that reduces the computation of spatial conduction activity to a diagonalization. It is shown that for low‐density amorphous carbon, connected sp²...
Article
New glass systems of bismuth borate with various concentrations of cadmium oxide are prepared based on the melt‐quenching method. The X‐ray diffraction (XRD) reveals a fully amorphous structure of the prepared glasses (S1–S4), and the UV–vis results display good transparency (>50%) in the visible and near‐UV region. In addition, the radiation shiel...
Article
The current study shows a new attempt to develop gamma ray shielding glasses. The proposed glass is a borate‐base composition modified with sodium and cadmium oxides and different concentrations of bismuth oxide. Based on the melt‐quenching technique, we prepared four glass compositions of 20NaO‐15CdO‐ (65‐x)B2O3‐xBi2O3, where x=0, 10, 20 and 30 mo...
Article
In this paper, we present ab initio computer models of Cu-doped amorphous Ta2O5, a promising candidate for conducting bridge random access memory memory devices, and study the structural, electronic, charge transport, and vibrational properties based on plane-wave density-functional methods. We offer an atomistic picture of the process of phase seg...
Article
We explore a new glassy material for radiation shielding applications. Novel transparent and non-toxic Bi2O3–B2O3 glasses including different concentrations of CdO were prepared by the conventional melt quenching method. The prepared samples were characterized and analyzed by using various analytical tools (XRD, FTIR, Raman, DSC, and UV-Vis-NIR). A...
Preprint
Full-text available
In this paper, we present ab initio computer models of Cu-doped amorphous Ta2O5 , a promising candidate for Conducting Bridge Random Access Memory (CBRAM) memory devices, and study the structural, electronic, charge transport and vibrational properties based on plane-wave density functional methods. We offer an atomistic picture of the process of p...
Article
The current study is aimed to investigate the gamma ray and neutron shielding properties of the bismuth borate glass system with various concentration of cadmium oxide (0, 5, 10 and 15 mol%). The XRD spectra confirms the amorphous state of the prepared samples. A number of physical and mechanical properties (molar volume, oxygen molar volume, oxyge...
Preprint
Full-text available
Structurally disordered materials continue to pose fundamental questions, including that of how different disordered phases ("polyamorphs") can coexist and transform from one to another. As a widely studied case, amorphous silicon (a-Si) forms a fourfold-coordinated, covalent random network at ambient conditions, but much higher-coordinated, metall...
Article
Full-text available
The putative ground-state structures of 13-atom Cu and Ag clusters have been studied using ab initio molecular-dynamics (AIMD) based on density-functional theory (DFT). An ensemble of low-energy configurations, collected along the AIMD trajectory and optimized to nearest local minimum-energy configurations, were studied. An analysis of the results...
Article
Full-text available
Understanding the local atomic order in amorphous thin film coatings and how it relates to macroscopic performance factors, such as mechanical loss, provides an important path towards enabling the accelerated discovery and development of improved coatings. High precision x-ray scattering measurements of thin films of amorphous zirconia-doped tantal...
Article
We perform an ab initio modeling of amorphous copper-doped alumina (a−Al2O3:Cu), a prospective memory material based on resistance switching, and study the structural origin of electronic conduction in this material. We generate molecular dynamics based models of a−Al2O3:Cu at various Cu concentrations and study the structural, electronic, and vibr...
Article
A ternary glassy chalcogenide material, Ag 20 Ge 28 Se 52 , is analyzed for structural, electronic, vibrational, and ion dynamical properties. The structural analysis has revealed some interesting substructures, which are typically found only in Se-rich or Ge-rich materials. The radial distribution function of the Ag 20 Ge 28 Se 52 model illustrate...
Article
Full-text available
We present a computational study of void-induced microstructure in amorphous silicon (a-Si) by generating ultra-large models of a-Si with a void-volume fraction of 0.3%, as observed in small-angle X-ray scattering (SAXS) experiments. The relationship between the morphology of voids and the intensity of scattering in SAXS has been studied by computi...
Article
Full-text available
The structural, vibrational, and electronic properties of Ni40Pd40P20 bulk metallic glass have been studied using ab initio molecular-dynamics simulations and total-energy optimization. Structural analyses of the resulting ab initio models show the presence of a few to no P–P bonds and two main building blocks, consisting of tricapped trigonal pris...
Article
Full-text available
Amorphous materials are being described by increasingly powerful computer simulations, but new approaches are still needed to fully understand their intricate atomic structures. Here, we show how machine‐learning (ML)‐based techniques can give new, quantitative chemical insight into the atomic‐scale structure of amorphous silicon (a‐Si). We combine...
Article
Full-text available
Amorphous materials are being described by increasingly powerful computer simulations, but new approaches are still needed to fully understand their intricate atomic structures. Here, we show how machine‐learning (ML)‐based techniques can give new, quantitative chemical insight into the atomic‐scale structure of amorphous silicon (a‐Si). We combine...
Preprint
We perform an {\it ab initio} modeling of amorphous copper-doped alumina (a-Al$_2$O$_3$:Cu), a prospective memory material based on resistance switching, and study the structural origin of electronic conduction in this material. We generate molecular dynamics based models of a-Al$_2$O$_3$:Cu at various Cu-concentrations and study the structural, el...
Preprint
Full-text available
In this paper we infer the structure of Pd40Ni40P20 from experimental diffraction data and ab initio interactions using Force Enhanced Atomic Refinement (FEAR). Our model accurately reproduces known experimental signatures of the system and is more efficient than conventional melt-quench schemes. We critically evaluate the local order, carry out de...
Preprint
Full-text available
In this paper, we discuss the atomistic structure of two conducting bridge computer memory materials, including Cu-doped alumina and silver-doped GeSe$_3$. We show that the Ag is rather uniformly distributed through the chalcogenide glass, whereas the Cu strongly clusters in the alumina material. The copper-oxide system conducts via extended state...
Preprint
Full-text available
Amorphous materials are coming within reach of realistic computer simulations, but new approaches are needed to fully understand their intricate atomic structures. Here, we show how machine-learning (ML)-based techniques can give new, quantitative chemical insight into the atomic-scale structure of amorphous silicon (a-Si). Based on a similarity fu...
Article
Full-text available
Diffraction data play an important role in the structural characterizations of solids. While reverse Monte Carlo (RMC) and similar methods provide an elegant approach to (re)construct a three-dimensional model of noncrystalline solids, a satisfactory solution to the RMC problem is still not available. Following our earlier efforts, we present here...
Preprint
Full-text available
The structural, vibrational, and electronic properties of Ni$_{40}$Pd$_{40}$P$_{20}$ bulk metallic glass have been studied using ${\it ab\,initio}$ molecular-dynamics simulations and total-energy optimization. Structural analyses of the resulting ${\it ab\,initio}$ models show the presence of few to no P-P bonds and two main building blocks, consis...
Preprint
Full-text available
The putative ground-state structures of 13-atom Cu and Ag clusters have been studied using ${\it ab \: initio}$ molecular-dynamics (AIMD) simulations based on the density-functional theory (DFT). An ensemble of low-energy configurations, collected along the AIMD trajectory and optimized to nearest local minimum-energy configurations, were studied....
Preprint
Full-text available
We present a computational study of the void-induced microstructure in amorphous silicon ($\it a$-Si) by generating ultra-large models of $\it a$-Si with a void-volume fraction of 0.3$\%$, as observed in small-angle x-ray scattering (SAXS) experiments. The relationship between the morphology of voids and the intensity of scattering in SAXS has been...
Article
In this paper, we show that low density nano-porous amorphous carbon (a-C) consists of interconnected regions of amorphous graphene (a-G). We include experimental information in producing models, while retaining the power and accuracy of \textit{ab initio} methods with no biasing assumptions. Our models are highly disordered with predominant $sp^2$...
Article
Conducting bridge random access memory materials have special promise for FLASH memory, other applications beside, and also special potential for continued miniaturization. They are electronic materials of unique flexibility. Here, we offer new models of Cu‐doped alumina, and reveal qualitative differences in the behavior of transition metal ions i...
Article
We present a computational study of small-angle X-ray scattering (SAXS) in amorphous silicon ($a$-Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating ultra-large high-...
Article
Full-text available
Amorphous silicon (a-Si) models are analyzed for structural, electronic and vibrational characteristics. Several models of various sizes have been computationally fabricated for this analysis. It is shown that a recently developed structural modeling algorithm known as force-enhanced atomic refinement (FEAR) provides results in agreement with exper...
Article
Full-text available
In this paper, we offer large and realistic models of amorphous carbon spanning densities from 0.95 g/cm3 to 3.5 g/cm3 . The models are designed to agree as closely as possible with experimental diffraction data while simultaneously attaining a local minimum of a density functional Hamilto- nian. The structure varies dramatically from interconnecte...
Article
Full-text available
We present a force-biased Monte Carlo (FMC) method for structural modeling of the transition-metal clusters of Fe, Ni, and Cu with sizes of 13, 30, and 55 atoms. By employing the Finnis-Sinclair potential for Fe and the Sutton-Chen potential for Ni and Cu, the total energy of the clusters is minimized using the local gradient of the potentials in M...
Article
Full-text available
Recently determined atomistic scale structures of near-two dimensional bilayers of vitreous silica (using scanning probe and electron microscopy) allow us to refine the experimentally determined coordinates to incorporate the known local chemistry more precisely. Further refinement is achieved by using classical potentials of varying complexity; on...
Article
Phonon lifetime in materials is an important observable that conveys basic information about structure, dynamics, and anharmonicity. Recent vibrational transient-grating measurements, using picosecond infrared pulses from free-electron lasers, have demonstrated that the vibrational-population decay rates of localized high-frequency stretching modes...
Article
Full-text available
Phonon lifetime in materials is an important observable that conveys basic information about structure, dynamics, and anharmonicity. Recent vibrational transient-grating measurements, using picosecond infrared pulses from free-electron lasers, have demonstrated that the vibrational-population decay rates of localized high-frequency stretching modes...
Article
Full-text available
We study an insulator-metal transition in a ternary chalcogenide glass (GeSe$_3$)$_{1-x}$Ag$_x$ for $x$=0.15 and 0.25. The conducting phase of the glass is obtained by using "Gap Sculpting" (Prasai et al, Sci. Rep. 5:15522 (2015)) and it is observed that the metallic and insulating phases have nearly identical DFT energies but have a conductivity c...
Article
We present a first-principles study of the formation and structure of microvoids in device-quality models of hydrogenated amorphous silicon (a−Si∶H). Using a combination of classical metadynamics and first-principles density-functional calculations, which is capable of generating large a−Si∶H models with a linear size of several nanometers and a re...
Article
In this paper, we present new computer models of low-density amorphous carbon, and study the structural, electronic and vibrational properties all based upon plane-wave density functional methods. The static structure factor and real space pair-correlation function is in agreement with available experimental data. We observe chains of sp bonded car...
Article
Full-text available
Density functional theory (DFT) calculations are carried out to study the structure and electronic structure of amorphous zinc oxide (a-ZnO). The models were prepared by the "melt-quench" method. The models are chemically ordered with some coordination defects. The effect of trivalent dopants in the structure and electronic properties of a-ZnO is i...
Article
We present a new approach to modeling materials. We show that Hellmann–Feynman forces associated with gap states may be used to drive the system to a preferred electronic structure that is also a total energy minimum. We use a priori information about the electronic gap to construct realistic models of tetrahedral amorphous carbon and silicon. We s...