2nd Workshop on ab initio phonon calculations
Speakers:
- G. Kresse, How phonon frequencies change upon partial inclusion of Fock exchange
- P. Blaha, Phonon calculations using WIEN2k
Scope:
Elementary lattice vibrations in solid materials are represented by phonons. To large extend these vibrations define thermal properties at finite temperature, hence they determine system thermodynamics. Phonon properties are modified by the presence of defects, disorder, grain boundaries, and show specific behaviour on surfaces, decorated surfaces, interfaces and amorphous systems. A deep understanding of phonons is specially exciting in systems exhibiting strong electron-phonon and/or magnetic-phonon couplings. Phonons are measured by a number of sophisticated techniques: inelestic coherent and incoherent neutron scattering, coherent x-ray scattering, nuclear inelastic scattering, infrared absorption, and raman scattering.
One method of calculating phonons in crystalline systems with appreciable accuracy is to use the Hellmann-Feynman forces found in ab initio calculations, based on supercell approach. The DFT ab initio codes, such as VASP, Wien2k, provide tools to derive complete sets of mentioned atomic forces. In this way the harmonic phonon properties of bulk crystals, without and with defects, surfaces, interfaces and similar systems can be treated. Furthermore, the quasiharmonic approximation allows to treat the mentioned systems at finite temperature, which is a necessary step for extending DFT results to describe the systems in a complete manner.