Functions in Phonon
PHONON
Phonon's options, which are listed below,
perform the following functions:
- Space Group & Unit Cell - selection of the crystallographic
space group, setting the lattice constants, lattice angles
and symmetry elements.
- 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
*.fdf as input files for optimizing and calculating the
necessery Hellmann-Feynman forces by
VASP,
or
SIESTA (e-mail: siesta@polar.fmc.uam.es)
softwares,
respectively.
There are small utilities to generate Hellmann-Feynman file from VASP.
SIESTA has option to calculate Hellmann-Feynman
file 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.
- Density of states - phonon density of states
and partial phonon density
of states for all atoms and all polarization directions are
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.
- 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.
- Report - ASCII file with all results of calculations.
Plots and intermediate data are additionaly
saved in several ASCII files.
Figues are isued either as HPGL2, or postscript file.
See: