Atomic structures of nonequilibrium alloys in an immiscible Co–Ag system
Tóm tắt
A Co–Ag potential in the form of TB-SMA (the second moment approximation of the tight-binding scheme) is derived based on some ab initio calculated physical properties. Applying the derived potential, molecular dynamics simulations reveal that a Co-/Ag-based solid solution retains its atomic homogeneity up to a critical ratio of9 Ag/12 Co at.%, over which the Ag/Co solute atoms begin to segregate. Correspondingly, a cage-like configuration is proposed to have 1 Ag/Co atom isotropically surrounded by 9 Co/7 Ag atoms for the homogeneous solid solution. Moreover, when the solute atoms exceed 12 Ag/18 Co at.%, the solid solution turns into an amorphous phase with inhomogeneous atomic structure.
Tài liệu tham khảo
Nonequilibrium Processing of Materials, edited by C. Suryanarayana (Elsevier Science, Amsterdam, The Netherlands, 1999).
F.R. deBoer, R. Boom, W.C. M. Mattens, A.R. Miedema, and A.K. Niessen, Cohesion in Metals: Transition Metal Alloys (North-Holland, Amsterdam, The Netherlands, 1989).
B.X. Liu, W.S. Lai, and Q. Zhang, Irradiation induced amorphiza-tion in metallic multilayers and calculation of glass-forming ability from atomistic potential in the binary metal systems, Mater. Sci. Eng.: Reports 29, 1 (2000).
B.X. Liu, W.S. Lai, and Z.J. Zhang, Solid-state crystal-to-amorphous transition in metal-metal multilayers and its thermo-dynamic and atomistic modeling, Adv. Phys. 50, 367 (2001).
J.H. He, H.W. Sheng, P.J. Schilling, C-L. Chien, and E. Ma, Amorphous structures in the immiscible Ag-Ni system, Phys. Rev. Lett. 86, 2826 (2001).
H.R. Gong, L.T. Kong, W.S. Lai, and B.X. Liu, Atomistic modeling of solid-state amorphization in an immiscible Cu-Ta system, Phys. Rev. B 66, 104204 (2002).
C. Tsang, R.E. Fontana, Jr., T. Lin, D.E. Heim, V.S. Speriosu, B.A. Gurney, and M.L. Williams, Design, fabrication and testing of spin-valve read heads for high-density recording, IEEE Trans. Magn. 30, 3801 (1994)
F. Ducastelle, in Computer Simulation in Materials Science, edited by M. Meyer and V. Pontikis (NATO Advanced Study Institute, Series E, 205, Kluwer, Dordrecht, The Netherlands, 1991).
D.J. Chadi, Surface atomic structures of covalent and ionic semiconductors, Phys. Rev. B 19, 2074 (1979).
F. Cleri and V. Rosato, Tight-binding potentials for transition metals and alloys, Phys. Rev. B 48, 22 (1993).
G. Kresse and J. Hafner, Ab initio molecular dynamics for liquid metals, Phys. Rev. B 47, 558 (1993).
J.B. Liu and B.X. Liu, Irradiation and interface induced formation of a nonequilibrium Ag3Co phase predicted by ab initio calculation, Phys. Rev. B 64, 4102 (2001).
M. Parrinello and A. Rahman, Polymorphic transitions in single crystals: A new molecular dynamics method, J. Appl. Phys. 52, 7182 (1981).
S.R. Phillpot, S. Yip, and D. Wolf, Anomalous temperature behavior of Sn impurities, Comput. Phys. 3, 20 (1989).
U. Ebels, R.L. Stamps, L. Zhou, P.E. Wigen, K. Ounadjela, J. Greggs, J. Morkowski, and A. Szajek, Induced phase shift in interlayer magnetic exchange coupling: Magnetic layer doping, Phys. Rev. B 58, 6367 (1998).
J.A. Morkowski and A. Szajek, Electronic band structure and calculated photoemission spectra of USi3 compound, Acta Phy-sica Polonica A 98, 5 (2000).
M. Gester, J.A.D. Matthew, S.M. Thompson, and G. Beamson, Electron spectroscopic evidence of metastable alloy formation of Ag and Au in Co, Phys. Rev. B 59, 15654 (1999).