Theory on the Trail of Vibrational STEM/EELS

The advent of monochromated STEM/EELS with energy resolution of a few meV plus either spatial or momentum-transfer resolution has enabled the detection of phonons and phonon polaritons at a wide range of temperatures.A new era of experimental investigations of vibrational properties of solids, two-dimensional materials, point and extended defects in solids and twodimensional materials, and nanostructures is now in full swing.Theory has always been a reliable companion to interpret data, complement data by probing beyond the reach of observations, and jointly unravel microscopic mechanisms that underly macroscopic phenomena and pertinent applications.The author, a practitioner of density-functional-theory calculations, has worked jointly with STEM microscopists for almost 30 years and has co-supervised joint STEM/theory Ph.D. theses.This talk will highlight the role of theory in joint EELS-Theory probing of the vibrational properties of materials and nanostructures: