"Anomalous" Debye-Waller Factor for bcc 4He

The Debye-Waller factor for bcc ⁴He is calculated at T=0 on the basis of a Hartree-Jastrow ground-state wave function by means of a cluster-expansion technique and is found to be a Gaussian function of the wave-vector transfer to within 1%. We discuss a possible reason for the large deviations from Gaussian behavior observed in recent neutron inelastic-scattering experiments.