Classical Interatomic Potential for Nb-Alumina Interfaces
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CLASSICAL INTERATOMIC POTENTIAL FOR Nb-ALUMINA INTERFACES K. Albe1,3 , R. Benedek2 , D. N. Seidman2 , R.S. Averback3 1
Institut f¨ur Materialwissenschaften, Technische Universit¨at Darmstadt, Petersenstr. 23, D-64287 Darmstadt, Germany 2 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA 3 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA ABSTRACT A modified-embedded-atom-method (MEAM) potential is derived for the ternary system Al-O-Nb in order to simulate the model oxide-metal interface sapphire-niobium. In the present work, MEAM parameters for Al and O given by Baskes were adopted, and the parameters for Nb are adjusted to match experimental data for pure Nb and calculated properties for Nb oxides and aluminides. The properties for niobium oxides and aluminides were obtained from localdensity-functional-theory (LDFT) calculations. The resultant potential was tested in simulations for the Nb(111)/α-alumina(0001) interface. MEAM predictions of the work of separation and the interlayer relaxations for two interface terminations are in excellent agreement with LDFT calculations. The MEAM potential therefore appears suitable for large-scale computer simulation of oxide-metal interface properties. INTRODUCTION Oxide-metal interfaces are prominent in a wide range of technological materials. They occur, for example, in oxide-coated structural alloys, light-bulb seals, metal-matrix composites, and catalyst supports, to mention a few. Structural modeling is an important tool for scientific investigations and for the engineering of such interfaces. Continuum modeling [1] can reveal certain structural features of interfaces, but cannot address the detailed chemical bonding characteristics at the interface. The atomistic modeling of oxide-metal interfaces [2] has lagged behind that of several other kinds of interfaces, for example, metal-metal, or oxide-oxide, because of the lack of suitable classical potentials. Although first-principles calculations are widely practiced for oxide-metal interfaces, they are restricted for computational reasons to static lattices and the coherent-interface approximation. In order to simulate entropic effects at high temperatures, mechanical properties, and misfit dislocations, a numerically efficient method is required. A strong motivation therefore exists to develop a classical potential that can describe the bonding both at the interface and in the bulk materials on either side of it. This has proven to be a difficult task, although for some neutral interfaces with relatively weak adhesion, the image-charge interaction model [3] has achieved some success. In this contribution, the modified-embedded-atom method [4, 5] is applied to a model oxide-metal interface that has received widespread attention, Nb-alumina [6, 7, 8]. The results indicate that this relatively simple potential scheme yields close agreement with first- principles calculations for the most widely investigated int
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