Fitting of accurate interatomic pair potentials for bulk metallic alloys using unrelaxed LDA energies
- National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)
We present a general and simple method for obtaining accurate, local density approximation (LDA-) quality interatomic potentials for a large class of bulk metallic alloys. The method is based on our analysis of atomic relaxation, which reveals that the energy released in the relaxation process can be approximated by calculating the epitaxially constrained energies of the constituents {ital A} and {ital B}. Therefore, the pair potential is fitted to the LDA-calculated epitaxial energies of the constituents (to capture the relaxation energies), and to the unrelaxed energies of ordered A{sub n}B{sub m} compounds (to capture the fixed-lattice {open_quotes}chemical{close_quotes} energy). The usefulness of our approach is demonstrated by carrying out this procedure for the Cu{sub 1{minus}x}Au{sub x} alloy system. The resulting pair potential reproduces the relaxed LDA formation energies of ordered compounds rather accurately, even though we used only unrelaxed energies as input. We also predict phonon spectra of the elements and ordered compounds in very good agreement with the LDA results. From the calculations for {approx}10000 atom supercells representing the random alloy, we obtain the bond lengths and relaxation energies of the random phase that are not accessible to direct LDA calculations. We predict that, while in Cu-rich alloys the Cu-Cu bond is shorter than the Cu-Au bond, at higher Au compositions this order is switched. Furthermore, we find that Au-rich Cu{sub 1{minus}x}Au{sub x} alloys have ground states that correspond to (001) superlattices of {ital n} monolayers of fcc Au stacked on {ital m} monolayers of the L1{sub 0} CuAu-I structure. The potential developed in this work is available at the site http://www.sst.nrel.gov/data/download.html for interested users. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 351902
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 60, Issue 3; Other Information: PBD: Jul 1999
- Country of Publication:
- United States
- Language:
- English
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