A First-Principles Study of Short Range Order in Cu-Zn

1989 ◽  
Vol 166 ◽  
Author(s):  
M. Sluiter ◽  
P.E.A. Turchi ◽  
D.D. Johnson ◽  
F.J. Pinski ◽  
D.M. Nicholson ◽  
...  
Keyword(s):  
First Principles ◽  
Short Range ◽  
Short Range Order ◽  
Alloy System ◽  
Cluster Variation Method ◽  
Range Order ◽  
Variation Method ◽  
Effective Pair ◽  
Cluster Variation ◽  
Pair Interactions

Recently, measurements of short-range order (SRO) diffuse neutron scattering intensity have been performed on quenched Cu-Zn alloys with 22.4 to 31.1 atomic percent (a/o) Zn, and pair interactions were obtained by Inverse Monte Carlo simulation [1]. These results are compared to SRO intensities and effective pair interactions obtained from first-principles electronic structure calculations. The theoretical SRO intensities were calculated with the Cluster Variation Method (CVM) in the tetrahedron-octahedron approximation with first-principles pair interactions as input. More generally, phase stability in the Cu-Zn alloy system is discussed, using ab-initio energetic properties.

High Temperature Measurements of Neutron Diffuse Scattering in a FeAll9.Sat% Single Crystal. Influence of Magnetism on Chemical Order.

1990 ◽  
Vol 213 ◽  
Author(s):  
V. Pierron-Bohnes ◽  
M.C. Cadeville ◽  
O. Schaerpf ◽  
A. Finel
Keyword(s):  
Diffuse Scattering ◽  
Short Range ◽  
Short Range Order ◽  
Magnetic Coupling ◽  
Pair Interaction ◽  
Cluster Variation Method ◽  
Range Order ◽  
Variation Method ◽  
Ferromagnetic Phase ◽  
Effective Pair

ABSTRACTThe influence of magnetism on atomic short range order is shown in a single crystalline FeAl19.sat% alloy in the disordered phase. The short range order has been measured in the paramagnetic state between 973 and 1573 K on D7 at ILL through neutron diffuse scattering in the [110] plane. The effective pair interaction potentials V1 , V2, V3 and V5 are calculated through an inverse cluster variation method. The results are compared to those obtained through X-ray diffuse scattering on the same alloy frozen in the ferromagnetic order state at 772 K. The effect of magnetic coupling on the atomic order is the most important on the 1st effective potential, which is smaller by about a factor 2 in the ferromagnetic phase than in the paramagnetic one.

scholarly journals First-Principles Study of Intermetallic Phase Stability in the Ternary Ti-Al-Nb Alloy System

1994 ◽  
Vol 364 ◽  
Author(s):  
Mark Asta ◽  
Alim Ormeci ◽  
John M. Wills ◽  
Robert C. Albers
Keyword(s):  
First Principles ◽  
Intermetallic Phase ◽  
Alloy System ◽  
Cluster Variation Method ◽  
Ternary Alloys ◽  
Interaction Parameters ◽  
Variation Method ◽  
Cluster Variation ◽  
The Stability ◽  
Alloy Thermodynamic

AbstractThe stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong ordering tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti2AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.

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