Q. H. Khan

Debye-Waller factors and Debye temperature of ZnTe

Accurate measurements were made to determine the Debye temperature and Debye-Waller factors for powder ZnTe by the method of elastic neutron diffraction, using a triple-axis neutron spectrometer. Measurements were made with neutrons of wavelength 1.17 A and corrections were made for the thermal diffuse scattering. The values of the Debye-Waller factors are BZn = 1.26 (5) and BTe = 0.74 (5) A2. The mass-weighted mean value \bar B is 0.91 (5) A2 which corresponds to a Debye temperature Θ = 198 (5)K. The results are in good agreement with the values determined by Cooper, Rouse & Fuess [Acta Cryst. (1973), A29, 44-56] using single-crystal neutron diffraction techniques.

Debye–Waller coefficient of KCl by the powder neutron diffraction method

The neutron diffraction pattern of powdered KCl has been measured using the triple-axis spectrometer both in the double-axis and the triple-axis modes. The thermal diffuse scattering (TDS) correction, which is very important in the double-axis pattern, is essentially eliminated in the triple-axis mode. Theoretical calculations are presented which give the relative TDS correction for the two cases by calculating the energy distribution of TDS. The Debye-Waller coefficient B using the triple-axis data is found to be (2.17 ± 0.16 A2), which is in agreement with the TDS-corrected values of other workers.

Temperature factor of silicon by powder neutron diffraction

The temperature factor of silicon has been determined by the powder neutron diffraction technique employing a double-axis neutron diffractometer. A neutron wavelength of 1.184 A was used in the experiment. The sample used was a fine powder of silicon of purity 99.999%. The correction to the observed intensities due to thermal diffuse scattering (TDS) was not applied as the neutron velocity of 3.34 km s-1 (corresponding to neutron wavelength of 1.184 A) is less than the minimum velocity of sound in this crystal. The B value obtained from these experiments was found to be 0.45 (2) A, corresponding to a mean-square vibrational amplitude of 0.017 (2) A2 and to a Debye temperature of 531 (11) K at the sample temperature of 284 K at which the experiment was performed.

The Debye–Waller factor of KBr by powder elastic neutron diffraction

The Debye-Waller parameter B of KBr has been determined by triple-axis neutron diffraction with a powder sample. Calculations have also been made to find the contributions of TDS to the diffraction peaks obtained by this technique and they were found to be negligible as expected. The B value thus found is 2.33 ± 0.09 A2.

Debye–Waller coefficient of Nb by the elastic neutron diffraction method

The Debye-Waller exponent B and the Debye temperature Θ for niobium have been determined at room temperature by the elastic neutron diffraction method using a triple-axis neutron spectrometer. The contribution of TDS to the diffraction peaks was found to be negligible. The value of B thus found was 0.55 (5) A2. The Debye temperature Θ was 262 (12) K. The results are compared with values obtained by other techniques.

The Debye–Waller parameter () of TlCl by powder elastic neutron diffraction

The mean Debye-Waller parameter {\bar {\it B}}of TlCl has been determined by double- as well as triple-axis neutron diffraction for a powder sample. Thermal diffuse scattering (TDS) corrections have also been made to the intensity of the diffraction peaks obtained by these techniques. TDS was found negligible in the triple-axis diffraction pattern as expected. The {\bar {\it B}} values thus found are 3.08 ± 0.43 and 3.07 ± 0.22 A2, respectively, for double- and triple-axis methods. These values are in good agreement with those found by recent X- ray diffraction measurements.