Orientational disorder in ammonium chloride: elastic diffuse neutron scattering with a new technique

Abstract

Elastic diffuse neutron scattering intensity due to orientational disorder in ND4Cl at room temperature, space group Pm3m, is studied with a single crystal. By a novel `vertical' energy analysis on the one hand and the `flat-cone' technique on the other, the intensity is obtained in a large three-dimensional region of reciprocal space in a reasonable time. The data are analysed with short-range-order and interaction-potential parameters. The two parameter sets are consistent. Local chlorine displacements of 0.16 Å, along 〈111〉 directions are determined.