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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. A new method for development of bondorder potentials for transition bcc metals
 Modelling and simulation in materials science and engineering 22 (2014), Nr.3, Art.034002, 22 S. ISSN: 09650393 (print) ISSN: 1361651X (online) 
 Deutsche Forschungsgemeinschaft DFG MR 22/51 
 European Commission EC FP7NMP; 263335; MULTIHY 

 Englisch 
 Zeitschriftenaufsatz, Elektronische Publikation 
 Fraunhofer IWM () 
 transition metals; bond order; environment dependent repulsion; potential testing; potential transferability 
Abstract
A new development of numerical bondorder potentials (BOPs) for the nonmagnetic transition metals V, Nb, Ta, Cr, Mo and W is presented. The principles on which the BOPs have been set up are the same as in earlier developments (Aoki et al 2007 Prog. Mater. Sci. 52 154). However, the bond integrals are based on the recently advanced method of parametrization of tightbinding from DFT calculations (Madsen et al 2011 Phys. Rev. B 83 4119, Urban et al 2011 Phys. Rev. B 84 155119) and do not require any screening. At the same time, the functional form of the environmentally dependent repulsion is identified with the functional form of the repulsion arising from the overlap of s and p electrons in argon as proposed in Aoki and Kurokawa (2007 J. Phys.: Condens. Matter 19 136228). This is justified by the same physical origin of the environment dependent repulsion, which in transition metals arises from the overlap of s electrons that are being squeezed into the ion core regions under the influence of the strong covalent d bonds. The testing of the developed BOPs involves investigation of alternative higher energy structures, transformation paths connecting the bcc structure with other structures via continuously distorted configurations, evaluation of the vacancy formation energy and calculation of phonon spectra. In all cases, the BOP calculations are in more than satisfactory agreement with either DFT calculations and/or available experimental data. The calculated γsurfaces for {1 0 1} planes all suggest that the core of 1/2〈1 1 1〉 screw dislocations is nondegenerate in the transition metals. This is also in full agreement with available calculations that account fully for the quantummechanical nature of the d electrons that provide the bulk of the bonding in transition metals. The testing of developed BOPs clearly demonstrates that they are transferable to structures well outside the regime of the ideal bcc lattice and are suitable for investigating the atomic structure and behaviour of extended crystal defects.