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X‐ray study of diffuse scattering in Ni–20 at% Cr
Author(s) -
Schönfeld B.,
Ice G. E.,
Sparks C. J.,
Haubold H.G.,
Schweika W.,
Shaffer L. B.
Publication year - 1994
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221830105
Subject(s) - scattering , monte carlo method , neutron scattering , lattice (music) , reverse monte carlo , x ray , materials science , atomic physics , physics , molecular physics , condensed matter physics , crystal structure , chemistry , crystallography , neutron diffraction , optics , mathematics , statistics , acoustics
A single crystal of Ni–20 at% Cr aged at 744 K for 480 h, similar to the case of a previous neutron scattering experiment, is investigated by diffuse X‐ray scattering using X‐rays at three different wavelengths, λ = 0.2075 nm (5975 eV), 0.1489 nm (8327.2 eV), and 0.1531 nm (8097 eV). The short‐range order and displacement scattering are separated based on the 3λ method recently introduced as well as on the Georgopoulos‐Cohen method. Both evaluation schemes yield similar Warren‐Cowley short‐range order parameters with less agreement in the individual static atomic displacements. The nearest‐neighbor displacement obtained by the 3A method for NiCr pairs, is consistent with a simple phenomenological model in which the Cr atoms expand the Ni lattice in a short‐range ordered alloy. Effective pair interactions calculated from model crystals using the inverse Monte Carlo method are found to be larger than previously deduced from neutron scattering experiments. If these pair interactions are used in Monte Carlo simulations to calculate the transition temperature T 0 of Ni 2 Cr, T 0 is underestimated compared with direct experimental findings.