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First Principles Force Field for Metallic Tantalum

Strachan, Alejandro and Çağin, Tahir and Gülseren, Oğuz and Mukherjee, Sonali and Cohen, Ronald E. and Goddard, William A., III (2002) First Principles Force Field for Metallic Tantalum. . (Unpublished)

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We propose a general strategy to develop accurate Force Fields (FF) for metallic systems derived from ab initio quantum mechanical (QM) calculations; we illustrate this approach for tantalum. As input data to the FF we use the linearized augmented plane wave method (LAPW) with the generalized gradient approximation (GGA) to calculate: (i) the zero temperature equation of state (EOS) of Ta for bcc, fcc, and hcp crystal structures for pressures up to ~500 GPa. (ii) Elastic constants. (iii) We use a mixed-basis pseudopotential code to calculate volume relaxed vacancy formation energy also as a function of pressure. In developing the Ta FF we also use previous QM calculations of: (iv) the equation of state for the A15 structure. (v) the surface energy bcc (100). (vi) energetics for shear twinning of the bcc crystal. We find that withappropriate parameters an embedded atom model force field (denoted as qEAM FF) is able to reproduce all this QM data. Thus, the same FF describes with good accuracy the bcc, fcc, hcp and A15 phases of Ta for pressures from ~ -10 GPa to ~ 500 GPa, while also describing the vacancy, surface energy, and shear transformations. The ability of this single FF to describe such a range of systems with a variety of coordinations suggests that it would be accurate for describing defects such as dislocations, grain boundaries, etc. We illustrate the use of the qEAM FF with molecular dynamics to calculate such finite temperature properties as the melting curve up to 300 GPa; we obtain a zero pressure melting temperature of T_(melt)=3150 +/- 50 K in good agreement with experiment (3213-3287 K). We also report on the thermal expansion of Ta in a wide temperature range; our calculated thermal expansivity agrees well with experimental data.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Strachan, Alejandro0000-0002-4174-9750
Çağin, Tahir0000-0002-3665-0932
Cohen, Ronald E.0000-0001-5871-2359
Goddard, William A., III0000-0003-0097-5716
Additional Information:This research was funded by a grant from DOE-ASCI-ASAP (DOE W-7405-ENG-48). The facilities of the MSC are also supported by grants from NSF (MRI CHE 99), ARO (MURI), ARO (DURIP), NASA, Kellogg, Dow Chemical, Seiko Epson, Avery Dennison, Chevron Corp., Asahi Chemical, 3M, GM, and Beckman Institute. Thanks to D. Singh and H. Krakauer for use of their LAPW code. We also thank Per Söderlind and John Moriarty for providing us with LMTO data. Computations were partially performed on the Cray SV1 at the Geophysical Laboratory, supported by NSF grant EAR-9975753 and the W. M. Keck Foundation.
Funding AgencyGrant Number
Department of Energy (DOE)W-7405-ENG-48
Army Research Office (ARO)UNSPECIFIED
Dow Chemical CompanyUNSPECIFIED
Chevron CorporationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Classification Code:PACS: 64.30.+t, 62.20.Dc, 64.70.-p, 64.70.Dv, 65.40.-b
Record Number:CaltechAUTHORS:20190702-100852563
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96879
Deposited By: Tony Diaz
Deposited On:08 Jul 2019 17:28
Last Modified:23 Nov 2020 23:44

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