We carried out neutron diffuse scattering on single crystals of disordered Ni3V, Ni2V, Ni3Cr and Ni2Cr. Intensity maxima show up at (1 1 2 0) . The potentials found using inverse CVM, with interactions including 4th neighbors, are temperature independent. Results are in agreement with electronic structure calculations, except in the Ni-Cr system. The transition temperature calculated from the Ni2Cr is half the experimental value (neglected interactions?).

In situ diffuse scatterings of neutrons on binary alloys

Order-disorder transitions are frequent in alloys The homogeneous ordered phase characterized by long-range order parameters which vanish in the disordered phase In fact, local order parameters can also be defined on a scale large enough compared to the size of the relevant unit cells, and they vary in space in the presence of defects

Thermodynamics of Surfaces and Interfaces

The fcc Pd-V phase diagram is computed by means of a Monte Carlo simulation with pair and multiplet interactions up to the fourth nearest neighbor distance. The Monte Carlo simulation was made faster by sampling the configuration on small clusters around each lattice point.

Ab Initio Computation Of The Fcc Pd-V Phase Diagram

The Monte Carlo technique was used to calculate the phase diagram of the fcc superstructures in the Pd-V system using up to fourth nearest neighbor, concentration independent, pair and multiplet interactions. The interactions were computed by the method of Direct Configurational Averaging using a Linearized Muffin-Tin Orbital Hamiltonian cast into the tight binding form. The phase diagram was computed with a fast Monte Carlo simulation technique using environment sampling. The two fcc ground states in experimental diagram are predicted to be stable. The computed transition temperatures are higher than those found experimentally.

An AB Initio Calculation of the Pd-V FCC Superstructure Phase Diagram with Fourth Nearest Neighbor Cluster Interactions

The order or segregation properties of compounds or solid solutions are important ingredients of the phase diagrams. If the order can be described as an atomic distribution on an underlying lattice, and if the interactions can be expressed in terms of pairs and other multiplet potentials between the atomic species, phase diagrams should be deducible from these potentials, along with other properties, such as antiphase boundaries, core structures of the dislocations in ordered compounds&; This approach, i.e. the very existence of the potentials, is legitimated by electronic structure calculations for or alloys of normal [1] and transition metals [2]. The G.P.M. (General perturbation Method) allows indeed to develop the order energy in terms of interatomic potentials, the reference state, namely the random alloy, being calculated within the C.P.A. (Coherent Potential Approximation).

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400372803

Phase Diagrams and Diffuse Neutron Scattering

We have shown that the difficulties met to determine interactions in the case of Pd3V is related to the nature of the system. The degeneracy of this system implies instabilities in the inverse procedure that leads to the interactions.We have pointed out that the parameter, responsible for the degeneracy if any, is known with a good accuracy and appears as the pertinent parameter.

Francine Solal

Papers

Phase Diagrams and Diffuse Neutron Scattering

The Origin of Poorly Conditioned Susceptibility Matrix Within Inverse CVM Algorithm in the Case of PD3V: A Comparison to the Case Of NI3V.