Diffuse intensity from phonon noise in inelastic neutron scattering

CN Saunders and VV Ladygin and DS Kim and CM Bernal-Choban and SH Lohaus and GE Granroth and DL Abernathy and B Fultz, PHYSICAL REVIEW MATERIALS, 9, 024602 (2025).

DOI: 10.1103/PhysRevMaterials.9.024602

Atomic vibrational dynamics in cuprite Cu2O was studied by inelastic neutron scattering and molecular- dynamics (MD) simulations from 10 K to 900 K. At 300 K, a diffuse inelastic intensity (DII) appeared in the phonon dispersions, and dominated the spectral intensity at higher temperatures. Classical MD simulations with a machine-learning interatomic potential reproduced general features of the DII. Better agreement with experiment was obtained with the addition of a stiffer potential at close approaches of the Cu and O-atoms. The DII originates from random phase shifts of vibrating O atoms that have brief ('10 fs) anharmonic interactions with neighboring Cu atoms. The spectrum of DII gives information about the interaction time of anharmonic interactions between atoms, and its intensity gives a strength of coupling between vibrating atoms and a thermal bath.

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