Diffuse scattering in decagonal Al-Ni-Fe

Significant diffuse scattering close to Bragg reflections was observed in decagonal Al71.5Ni23.5Fe5 phase which is otherwise free of disorder phenomena. As found by synchrotron measurements (DESY, RASYLAB) this diffuse scattering is anisotropically distributed and dumb-bell shaped with a major extension parallel to the scattering vector Q and a typical 1/q(2) fall-off of the diffuse wings. The diffuse data were tentatively interpreted in frame of a TDS theory [Phys. Rev. B 59 (1999) 8221 using only 2 (out of 5) phonon elastic constants, c(11) and c(66). A remarkable matching of observed and calculated diffuse data could be achieved, however, with an unusual (?) c(66)/c(11) ratio equal to 4.0. An alternative interpretation is based on strain fields caused by static lattice distortions [Phys. Rev. B 37 (1988) 4458]. Possibly there is a superposition of both contributions. (C) 2002 Elsevier Science B.V. All rights reserved.