Diffuse scattering from solid solutions: Real-space versus reciprocal-space data evaluation and electronic structure calculations

Elastic diffuse scattering from six concentrated binary fcc alloys in states of thermal equilibrium, previously analyzed within the real-space approach introduced by Borie and Sparks, was reevaluated within the reciprocal-space approach of Krivoglaz and Khachaturyan. Size effect scattering was treated within the microscopic theory of elasticity. Chemical and strain-induced interaction parameters were least-squares fitted to yield short-range order (SRO) scattering and size effect (SE) scattering. The r-values in fitting were larger for the reciprocal space than for the real-space approach, as demonstrated for the neutron scattering studies. While SRO scattering and thus the effective pair interaction (EPI) parameters well agree with the real-space approach, SE scattering differs, especially close to Bragg reflections, unless the strain-induced displacement fields are treated with a cutoff in range. The separation of the EPI parameters into the chemical and strain-induced interaction parameters shows similarity with the data from electronic structure calculations. Monte Carlo simulations with total interaction parameters closely reproduce SRO scattering.