NEUTRON-SCATTERING FROM VITREOUS SILICA .4. TIME-OF-FLIGHT DIFFRACTION

The optimum configuration for a neutron time-of-flight diffractometer to study amorphous solids is discussed and it is concluded that measurements should be performed at relatively low scattering angles using a cold moderator. Good reciprocal space resolution is also important. Time-of-flight data for vitreous silica are combined with twin-axis data from part II (P.A.V. Johnson et al., J. Non-Cryst. Solids 58 (1983) 109) to give an accurate composite interference function and excellent real space resolution on Fourier transformation. The maximum scattering vector, Qmax, is 45.2 A ̊-1. A peak fit to the resulting correlation function yields a mean SiO bond length of 1.608±0.004 A ̊. © 1990.