Functions in Phonon
PHONON Software version 3.11
Phonon's options
perform the following functions:
- Space Group & Unit Cell - selection of the
crystallographic space group, setting the lattice constants, lattice
angles and symmetry elements. All 230 space groups are given in
International Tables for Crystallography (1989) setting, and in Kovalev
(1965) setting.
- Particle Positions - position of atoms (or molecules) in
the crystallographic unit cell, selection of active degree of freedom,
atomic masses. Construction of the crystal structure from
non-equivalent positions of atoms.
- Moments of Inertia - moments of inertia for molecules.
- Electric Charges - effective electric charges,
dielectric constant. Selection of parameters to model the longitudinal
optic phonon branchs close to LO/TO splitting.
- Crystal Viewer - A view of the crystal unit cell and
supercell.
- Interaction Range / Coordination Shells - number of
coordination shells taken into account in construction of the dynamical
matrix. Calculation of neighbor list, symmetry of force constants
matrices and number of independent force constant parameters.
- Interaction Range / Supercell - supercell matrix, which
limits the interaction range to the coordination shells inside the
supercell. Any shape of supercell can be used. If the supercell breaks
the space group symmetry then the lower space group symmetry is
accepted. Here are calculated the neighbor list, symmetry of force
constants matrices and the numbers of independent force constant
parameters. A set of displacements needed to calculate the
Hellmann-Feynman forces for the direct method is proposed. A file with
positions of all atoms of the supercell can be isued
- Interaction Range / Show Position File - generates
POSCAR, or similar input files for optimizing and calculating the
necessery Hellmann-Feynman forces by VASP, Wien2k, or Siesta softwares. There are
small utilities to generate Hellmann-Feynman file from VASP. Wien2k and
Siesta have options to calculate Hellmann-Feynman forces ready to
import to Phonon.
- Hellmann-Feynman File / Supercell - supercell matrix
used in ab initio calculations.
- Hellmann-Feynman File / Tranlational - Rotational
Invariances - imposes on the force constants, which are derived
with the direct method, the translational - rotational invariances.
Then, acoustic modes start at zero frequency.
- Import H-F File - import of the file with
Hellmann-Feynman forces calculated by an ab initio program.
Derives the force constant matrices from the suplied Hellmann-Feynman
forces using the direct method.
- Plot Force Constants - plot of the amplitude of the
force constant elements as a function of distance. This demonstrates
the decay of potential interaction with distance.
- Potential Parameters - a formular to introduce the
values of independent parameters of the force constants.
- Potential Parameters / Set Invariances - for some
high-symmetry crystals it allows to impose the translational-rotational
invariances even when force constants were introduced by hand.
- Dispersion curves / Set Points /Wave Vectors - builds
the dynamical matrix, and calculates the phonon dispersion curves along
any set of straigth lines in reciprocal space. The lines are specified
by an arbitrary list of wave vectors. Complex polarization vectors
and/or real displacement vectors can be calculated for any phonon mode.
The program finds the irreducible representations for all phonon modes
at the Brillouin zone center.
- Plot dispersion curves - plot of a figure of dispersion
curves.
- Plot form factors of dispersion curves - plot of a
figure of coloured dispersion curves, where the colour is proportional
to a form factor being proportional to square of polarization vector of
a given mode.
- Density of states - phonon density of states and partial
phonon density of states for all atoms and all polarization directions
calculated by Monte Carlo sampling of the Brillouin zone.
- Plot density of states - plot of a figure of total and
partial density of states for any atom and/or direction.
- Thermodynamic Functions/Plot Internal Energy - plot of
internal energy as a function of temperature.
- Thermodynamic Functions/Plot Free Energy - plot of free
energy as a function of temperature.
- Thermodynamic Functions/Plot Entropy - plot of entropy
as a function of temperature.
- Thermodynamic Functions/Plot Heat Capacity - plot of
heat capacity at constant volume as a function of temperature.
- Thermodynamic Functions/Plot Thermal Displacemnts - plot
of the tensors of thermal displacements, related with the Debey-Waller
factors, for all atoms in the unit cell, as a function of temperature.
- Dynamical Structure Factor - plot of intensity of the
coherent neutron scattering in different Brillouin zones and different
geometries.
- Neutron Scattering/Incoherent on Monocrystal - plot of
doubly differential incoherent inelastic neutron scattering cross
section of one-phonon processes from the monocrystal.
- Neutron Scattering/Incoherent on Polycrystal - plot of
doubly differential incoherent inelastic neutron scattering cross
section of one-, two-, ... five-phonon processes from the polycrystal.
- Import model - opens a project from about 55
predetermined models with realistic force constants, or
Hellmann-Feynman files.
See: