Workshop on ab initio phonon calculations
Prelegenci:
- G.Kresse, VASP: Accurate force calculations and VASP-PAW datasets.
- P.Blaha, Electronic structure, atomic forces and structural relaxations by WIEN2k.
- K.Parlinski, Calculation of phonons and thermodynamic properties of crystals by Phonon.
- M.Johnson, Phonons in molecular crystals - from ab initio calcultions to neutron scattering, X-ray and infra-red data.
Tematyka:
Phonons are the fundamental description of vibrations in solid state materials, and to a large extend they define the finite temperature properties of solids. They play an important role for quite a number of microscopic and bulk phenomena such as inelastic coherent and incoherent neutron scattering, coherent inelastic X-ray scattering, inelastic nuclear absorption, infrared absorption, raman scattering, thermodynamic functions, Debye-Waller factor, thermal expansion, temperature dependence of mechanical, magnetic properties, phase transitions, phase diagrams, and chemical reactions. A deep understanding of phonon behaviour, especially that of new materials, is a necessary condition for future technological developments. In surfaces, interfaces, multilayers, crystals with defects and impurities, etc. the role of phonons has not yet been studied and fully understood and ab initio studies of phonons in these systems are very limited, if existing at all.
One way of treating phonons in crystalline systems is to use the Hellmann-Feynman forces calculated for specifically perturbed supercells. During the Workshop the participants learn about numerical tools, which allow to carry out ab initio phonon calculations for the above mentioned systems. The purpose of this workshop is to offer an introduction to the fundamentals of phonon calculations performed on the basis of data derived with either VASP or the Wien2k programs. Using the Phonon program, phonon frequencies and related quantities can be computed. Many examples of phonon calculated with supercells, often including more than 100 atoms, will be presented. Bulk crystals, even complex ones, require less computational effort, while defected crystals, and lower dimensional systems, having less symmetry, need considerable computer power. Since these calculations can be parallelized, the cluster facilities can be effectively used for this purpose. Moreover, the finite temperature calculations, carried out, for example, within the quasiharminic approximation, require repeating many similar runs for slightly different parameter, like pressure. Thus, using the above numerical tools and computer cluster technique we are just facing the moment to handle effectively from first-principles the finite temperature properties of most crystalline systems.
The speakers are mostly members of the organizing team, plus current Phonon/VASP/Wien2k users presenting selected applications.
Uczestnicy:
The workshop was intended for participants who were willing to enhance their knowledge of Phonon/VASP/Wien2k techniques. The fields represented included: materials engineering, mineralogy, geophysics as well as experimental physics and chemistry.