Dispersion Bands Here are shown the result of anharmonic phonon calculations obtained for phonon dispersion relations. It is seen that the phonon curves are widen to phonon bands with relevant width and shape. These bands can be plot as a colour maps, where colour denote the intensity of a given pixel belonging to the band. Each colour point represents the intensity collected close to a given pixel. The scale of colours runs from 0% to 100%. In reciprocal space the wavevector path can be selected along any lines. PbTe.The colour maps on FIGURE.1. represent the computed at several temperatures T, the anharmonic dispersion bands of cubic lead telluride PbTe. Intensities are given by the colours of the same legend as for MgSiO_{3,} maps below.
FIGURE.1. Plots of intensity maps of anharmonic phonon dispersion curves of cubic PbTe at several temperature T. MgSiO_{3,}.The phonon dispersion curves and the map of phonon dispersion bands (colour map), FIGURE.2, correspond to crystal of magnesium silicate MgSiO_{3,}. The crystal has orthorhombic structure of space group Pmnb, with 20 atoms in primitive unit cell. For computation, the unit cell was doubled to supercell 1x1x2 with 40 atoms. The anharmonic calculations were performed at temperature T=2300K and pressure P=57GPa, corresponding approximatelly to Earth depth of 2500km. The wavevector pathes are the same on both plots.
FIGURE.2. (Up) Plot of harmonic phonon dispersion curves of MgSiO_{3}. (Down) Intensity map of anharmonic dispersion bands of MgSiO_{3} at temperature T=2300K and pressure P=57GPa. The colours represent the intensities from 0% to 100%. See the legend. Last update: September 20, 2017 |