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Metallurgy

University of Pennsylvania

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Articles 1 - 4 of 4

Full-Text Articles in Physics

Bond-Order Potential For Molybdenum: Application To Dislocation Behavior, Matous Mrovec, Duc Nguyen-Manh, David G. Pettifor, Vaclav Vitek Mar 2004

Bond-Order Potential For Molybdenum: Application To Dislocation Behavior, Matous Mrovec, Duc Nguyen-Manh, David G. Pettifor, Vaclav Vitek

Departmental Papers (MSE)

The bond-order potential (BOP) for transition metals is a real-space semiempirical description of interactions between the atoms, which is based on the tight-binding approximation and the d-band model. This scheme provides a direct bridge between the electronic level modeling and the atomistic modeling, where the electronic degrees of freedom have been coarse grained into many-body interatomic potentials. In this paper we construct BOP in which both the attractive and the repulsive contributions to the binding energy are environmentally dependent due to both the nonorthogonality of the orbitals and the breathing of the screening charges. The construction of the BOP ...


Interatomic Forces And Atomic Structure Of Grain Boundaries In Copper-Bismuth Alloys, Min Yan, Mojmír Šob, David E. Luzzi, Vaclav Vitek, Graeme J. Ackland, M. Methfessel, C. O. Rodriguez Mar 1993

Interatomic Forces And Atomic Structure Of Grain Boundaries In Copper-Bismuth Alloys, Min Yan, Mojmír Šob, David E. Luzzi, Vaclav Vitek, Graeme J. Ackland, M. Methfessel, C. O. Rodriguez

Departmental Papers (MSE)

The many-body empirical potentials that describe atomic interactions in the copper-bismuth system were constructed using both experimental data and physical quantities obtained by ab initio full-potential linear muffin-tin orbital calculations for a metastable Cu3Bi compound. These potentials were then used to calculate the structure of a grain boundary in copper containing bismuth, which was at the same time studied by high-resolution electron microscopy (HREM). Excellent agreement between the calculated and observed structures is shown by comparing a through-focal series of observed and calculated images. This agreement validates the constructed potentials, which can be used with a high confidence ...


Many-Body Potentials And Atomic-Scale Relaxations In Noble-Metal Alloys, Graeme J. Ackland, Vaclav Vitek May 1990

Many-Body Potentials And Atomic-Scale Relaxations In Noble-Metal Alloys, Graeme J. Ackland, Vaclav Vitek

Departmental Papers (MSE)

We derive empirical many-body potentials for noble-metal alloy systems in the framework of the Finnis-Sinclair model [Philos. Mag. A 50, 45 (1984)] which is based on a second-moment approximation to the tight-binding density of states for transition metals [F. Cyrot, J. Phys. Chem. Solids 29, 1235 (1968)]. The most important extension of the model is a simple incorporation of interspecies interactions which involves fitting the alloying energies. The importance of properly accounting for the local atomic relaxations when constructing the potentials is emphasized. The observed principal features of the phase diagrams of the alloys are all well reproduced by this ...


Radial Distribution Function And Structural Relaxation In Amorphous Solids, David J. Srolovitz, Takeshi Egami, Vaclav Vitek Dec 1981

Radial Distribution Function And Structural Relaxation In Amorphous Solids, David J. Srolovitz, Takeshi Egami, Vaclav Vitek

Departmental Papers (MSE)

A method of interpreting radial distribution functions (RDF) of amorphous metals is proposed in which the role of the local atomic structure is emphasized. It is found that the width and height of the peaks of the RDF are related to the second moment of the atomic-level hydrostatic stress distribution ⟨p2⟩. The results of this analysis are then used to explain the details of the changes that occur in the RDF when structural relaxation takes place. The theoretical ▵RDF is found to be in excellent agreement with the results of a computer study and previous experimental results. It is ...