Theoretical investigation of phase stability in non-magnetic Fe-V substitutional alloys
The assessed phase diagram of Fe-V exhibits a continuous high temperature bcc solid solution intersected at lower temperatures by a complex sigma phase centered around equiatomic composition. Slow kinetics of the bcc to sigma transformation make it possible to retain the bcc solid solution at low temperature. It has been observed that this metastable solid solution has a tendency to order with a CsCl type structure (B2) below 970 K. As a first attempt to describe this behavior from an electronic structure approach, this paper will study the phase stability on the bcc lattice using a realistic tight-binding Hamiltonian. Main features are as follows: Element and structure specific Slater-Koster parameters are used and lattice parameter effects are incorporated through scaling. Charge transfer is set to zero by rigidly shifting the onsite energies of one constituent. The Coherent Potential Approximation (CPA) is invoked with four levels corresponding to states with s, p, t{sub 2g} and e{sub g} like symmetry. Effects of off-diagonal disorder (ODD) have not been included, instead, an average alloy Hamiltonian was defined using the Slater-Koster parameters of the components weighted by concentration. At equiatomic composition the effect of this approximation has been evaluated by repeating the electronic structure calculation with inclusion of ODD effects. Effective pair interactions, as defined within the Generalized Perturbation Method (GPM), have been computed and have been used to evaluate the ground states of configurational order on the bcc lattice in the Fe-V system. Furthermore, the theoretically derived energetic properties have been used to determine the phase diagram pertaining to the (metastable) bcc lattice with the Cluster Variation Method (CVM) in the tetrahedron approximation. 11 refs., 4 figs., 1 tab.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- Sponsoring Organization:
- DOE/DP
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6292378
- Report Number(s):
- UCRL-JC-104593; CONF-901105-84; ON: DE91006711
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society, Boston, MA (USA), 24 Nov - 1 Dec 1990
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
IRON ALLOYS
PHASE STABILITY
VANADIUM ALLOYS
BCC LATTICES
CONFIGURATION INTERACTION
ELECTRONIC STRUCTURE
ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
STABILITY
360102* - Metals & Alloys- Structure & Phase Studies
640302 - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory