
Computed Properties
Phonon Software ver. 6.15 allows to calculate the following material properties:
 Phonon dispersion relations (PDR) ω(k,j),
 Existence of a soft mode, which indicates dynamical instability of the crystal,
and the relaxation path to lower symmetry phase.
In particular cases the soft mode could help to describe transition states, which
determine the diffusion constant.
 Coloured phonon dispersion relations, where the colour denotes
phonon intensity found via predefined filters.
A filter is a type of form factor and depends on polarization vectors.
 Transverse optic (TO) and longitudinal optic (LO) phonon modes at Γ
point. To all these modes an irreducible representations are assigned.
The LO modes show mixed representations in most of the cases.
 Animate vibrational motion of any phonon mode selected by mouse pointer.
 A displacement pattern for any phonon mode.
 A symmetry reduction caused by phonon mode belonging to commensurate
wave vector
and selected by mouse pointer.
 Search for most intense phonon mode across many Brillouin zones,
using definite filter.
 Phonon density of states (DOS) g(ω).
 Partial phonon density of states g_{μ,i}(ω)
for a specific atom μ moving along
idirection.
 Thermodynamical functions: internal energy E,
entropy S,
free energy F,
heat capacity at constant volume c_{v},
as a function of temperature T.
 Thermal mean square displacement tensor, or DebyeWaller factor as a function of temperature.
 Space group of the lowsymmetry structure caused by a condensation
of a multidimensional phonon soft mode, or any other combination of phonon modes,
for example such which
may strongly be coupled to electronic states.
 Intensity of the inelastic coherent neutron scattering of a given
phonon branch, and in selected Brillouin zone.
 Spectra of the inelastic incoherent neutron scattering for monocrystal
and polycrystal.
 Intensity of the inelastic xrays scattering of a given
phonon branch, and in selected Brillouin zone.
 Spectra of the inelastic nuclear scattering for monocrystal.
 Phononic part of the dielectric tensor.
 Vectors of mode effective charges for any direction of the unit vector of the
wavevector in vicinity Γ point.
 Frequencies of irreducible representations of TO and LO modes at Γ point. In particular,
the LO mode frequencies depends on the directions the wavevector points at Γ.
 Intensity of the infrared absorption spectra including LO/TO splittings.
 Intensity of the Raman scattering spectra including LO/TO splittings
(where relevant in noncentrosymmetric crystals).
Procedures in which Phonon Software must be used many times:
 Grüneissen parameters. Phonon frequencies should
be calculated as a function of pressure.
 Quasiharmonic approximation. Phonon frequencies should be
calculated as a function of negative and
positive pressures. Quasiharmonic approach relies on finding the scaling relation
between pressure (calculated in ab initio runs), and temperature (found
from a construction of
thermodynamical behaviour of the free energy). In this way pressure dependence of a
quantity is rescaled to temperature dependence.
Thermal expansion and temperaturepressure phase diagram can be
determined.
 Detection of electronphonon coupling. In these case electronic states must be
calculated for such supercell for which atoms are displaced according to a frozen phonon.
 Equilibrium parameters of chemical reaction with solid component.
Free energy of the solid component contains phonon contribution.
Systems to be treated in Phonon Software:
 Crystals classified by 230 crystallographic space groups.
 Surfaces, multilayers, and interfaces within the slab method,
if possible, using a crystallographic space group.
 Crystals with point defects. The space group must be modified in order
to account for the presence of defect.
Last update: July 20, 2014
