D B Sirdeshmukh
Articles written in Pramana – Journal of Physics
Volume 10 Issue 4 April 1978 pp 357-360 Crystallography
Integrated intensities of Bragg reflections of CdO, PbS and MnS have been measured at room temperature using an x-ray powder diffractometer. From a least square treatment of the intensity data the mean Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. Calculations were made using scattering factors pertaining to neutral atoms as well as doubly ionised ions. The results from the two sets of calculations agreed within limits of errors.
Volume 10 Issue 6 June 1978 pp 597-600 Crystallography
From the integrated intensities of Bragg reflections measured at room temperature with an x-ray powder diffractometer, the mean Debye-Waller factor
The energy of formation of a Schottky pair in these crystals has been estimated from an empirical relation between the x-ray Debye temperature and the energy of formation.
Volume 23 Issue 2 August 1984 pp 251-256 Instrumentation
The design of a simple inexpensive instrument which can be used along with a simple laboratory microscope to measure microhardness of crystals is described. The design is based on the fact that the lengths of arms of indentation dislocation rosette (
Volume 23 Issue 5 November 1984 pp 595-597 Solid State Physics
The integrated intensities of Bragg reflections are measured for AgCl and AgBr at room temperature using an x-ray powder diffractometer. The Debye-Waller factors and Debye temperatures are evaluated.
Volume 24 Issue 6 June 1985 pp 887-893 Solid State Physics
The hardness of NaCl and KCl crystals has been estimated from the lengths of dislocation rosette formed around indentation at various temperatures up to 400°C. The hardness decreases with increasing temperature. This is due to the softening of the crystals at elevated temperatures which results in the easy movement of dislocations. The results are discussed using a few available relations which connect hardness to temperature. Arms of indentation dislocation rosette are well defined up to 300°C but around 400°C the rosette pattern is spread over a circular region. A possible mechanism is discussed.
Volume 25 Issue 1 July 1985 pp 71-73 Solid State Physics
The integrated intensities of Bragg reflections have been measured for mixed crystals in the K
Volume 28 Issue 1 January 1987 pp 81-86 Solid State Physics
X-ray diffraction and colour centre studies have been carried out on RbCl-RbBr mixed crystals. The lattice constant closely follows the linear form of Vegard’s law. The mean Debye-Waller factor shows a highly nonlinear composition dependence. The composition dependence of the F-band peak position is slightly nonlinear but that of the F-band half-width is highly nonlinear. The Ivey-Mollow relation holds for this system with an index of 2.5. The ‘size effect’ is found to have a dominant effect on the F-band width.
Volume 29 Issue 6 December 1987 pp 583-588 Condensed Matter Physics
The lattice parameters of CdF2 and
Volume 31 Issue 3 September 1988 pp 221-224 Condensed Matter Physics
Integrated intensities of Bragg reflections have been measured for KCl-RbCl mixed crystals with various compositions and the data used to evaluate the mean Debye-Waller factors and the Debye temperatures. The composition dependence of the Debye-Waller factor is highly nonlinear with positive deviations from linearity while that of the Debye temperature is slightly nonlinear with negative deviations from linearity. Using an empirical relationship between the Debye temperature and the molar volume, the average values of the Gruneisen parameter for some mixed crystal systems are obtained.
Volume 34 Issue 2 February 1990 pp 151-156
Indentations have been made on the (111) planes of CaF2, SrF2 and BaF2 at various temperatures up to 700°C. By etching the crystals, the indentation dislocation rosettes (IDRs) have been recorded and the relative hardness is estimated from the dimensions of the IDRs. The hardness of all these crystals falls with temperature according to the equation
Volume 34 Issue 3 March 1990 pp 235-241
The melting points in the KCl-KBr, RbCl-RbBr and KBr-RbBr mixed crystal systems have been measured using the microscopic method. In all the three systems, melting points vary nonlinearly with composition, with negative deviations from linearity and maximum deviation at about the equimolar concentration. The observed composition dependence of the melting points is explained qualitatively in terms of the enhanced concentration of point defects and dislocations in mixed crystals.
Volume 38 Issue 6 June 1992 pp 681-683 Research Articles
X-ray powder diffractograms of EuS and EuTe have been recorded. The integrated intensites have been measured and corrected for TDS. From an analysis of the intensity data, Debye-Waller factors and Debye temperatures have been evaluated.
Volume 43 Issue 1 July 1994 pp 33-39
Mixed crystals of RbBr and RbI have been prepared from melt. Using an X-ray diffractometer powder patterns have been recorded. The lattice constants show slightly positive deviations from Vegard’s law. From the integrated intensities, the mean Debye-Waller factor has been determined. The Debye-Waller factor shows a highly non-linear composition dependence with positive deviations from linearity, the values for intermediate compositions exceeding those for the end members. The Debye temperatures calculated from the Debye-Waller factors show a non-linear composition dependence with negative deviations from linearity.
Volume 43 Issue 1 July 1994 pp 101-115
A high temperature X-ray powder diffraction camera has been designed and fabricated with indigenous material. The camera design is similar to the Unicam model but overcomes some inconvenient features of the latter. The camera incorporates a miniheater which is inexpensive and easily replaceable. The camera enables determination of lattice parameters with an accuracy of ±0.0002 Å up to 800°C.
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