Papers by Keyword: MEM

Abstract: An effort has been made to understand the charge density distribution of the Si and Ge based diluted magnetic semiconductors. A theoretical analysis has been done on the variation of charge densities when the semiconductors Si and Ge are doped with the transition metal atoms of V, Mn and Co with different concentrations of x (0.02, 0.04, 0.06, 0.08, and 0.10), in Si_1-xM_x and Ge_1-xM_x. Two dimensional electron density contour maps have been plotted for all the compositions studied in this work. The theoretical mid bond densities were found out for the compounds which can be taken as the reference values for comparison of the experimental values of the same compositions.

Abstract: The electron density distribution and the local structure of aluminum oxide (Al2O3), chromium doped aluminum oxide (Cr:Al2O3) and vanadium doped aluminum oxide (V:Al2O3) have been studied. Powder X-ray data set of Al2O3 , Cr:Al2O3 and V:Al2O3 is analyzed in terms of cell parameters, thermal vibration parameters, 1D, 2D and 3 Dimensional electron density distributions. The bonding between the atoms using the maximum entropy method (MEM) and bond length distribution using pair distribution function (PDF) has been analyzed. The particle size of Al2O3 , Cr:Al2O3 and V:Al2O3 is also analyzed using XRD and SEM.

Abstract: Tin oxide material (SnO2) is synthesized in nano scale range and is characterized. The refined X-ray intensity data was obtained from the Reitveld method. The electron density of nano SnO2 is determined using MEM (Maximum Entropy Method). Using one, two and three dimensional MEM maps, the bonding within the atoms is clearly understood. The particle size of SnO2 is also analyzed using XRD and SEM.

Abstract: The alkali halide Na1-xAgxCl, with two different compositions (x = 0.03 and 0.10), was studied with regard to the Ag impurities in terms of the bonding and electron density distribution. X-ray single crystal data sets have been used for the purpose. The present analysis focused on the electron density distribution and hence the interaction between the atoms is clearly revealed by maximum entropy method (MEM) and multipole analyses. The bonding in these systems has been studied using two-dimensional MEM electron density maps on the (100) and (110) planes and onedimensional electron density profiles along the [100], [110] and [111] directions. The mid-bond electron densities between atoms in these systems are found to be 0.175 e/Å3 and 0.183 e/Å3, respectively, for Na0.97Ag0.03Cl and Na0.90Ag0.10Cl. Multipole analysis of the structure has been performed for these two systems, with respect to the expansion/contraction of the ion involved.