ph_accessories is python module to calculate harmonic thermal properties by using DFT derived force constants. Currently support only exists for force constants derived in *.fc format using QUANTUM ESPRESSO.
ph_accessories(File_input)
Provides methods to calculate harmonic thermal properties
Input :
File_input :- Force constant file generated using Quantum Espresso.
Required file format is *.fc
This example shows how to calculate density of states for Si using the force constant file 'Si_q2.fc'
from ph_accessories import ph_accessories as ph
Si = ph('Si_q2.fc')
# Returns the density of states for Si, using a Mokhorst Pack grid with 0.1 q spacing and generated with frequency spacing of 1 THz
DOS, freq = Si.DOS(qspace = 0.1, wspace = 1e12) ph.ntyp --> Number of type of atoms in the unit cell (int)
ph.nat --> Number of atoms in the unit cell (int)
ph.ityp --> Array of size ph.nat, where ityp[na] is integer defining the type of atom
ph.at --> lattice vectors of the unit cell
ph.tau --> basis vectors of the unit cell
ph.amass --> mass of every atom in the unit cell. Array of size ph.ntyp
ph.omega --> Volume of unit cell
ph.epsil --> dielectric matrix
ph.frc --> Force constant tensor.
ph.bg --> Reciprocal lattice vectors
ph.recips()
Calculate reciprocal lattice vectors
return : ph.bg
ph.wsweight(r)
Weighting functions required to calculate dispersion relation
Please check : https://www.mail-archive.com/[email protected]/msg24388.html
for technical details
input : r - location vector in cartesian coordinate
return : weight
ph.set_ast(asr)
Acoustic sum rule
input : asr == 'simple'
return : self.frc, self.zeu
ph.frc_blk(q)
Calculate dynamic matrix on atom basis
input : q - wavevectors in cartesian coordinates
return : self.dyn
ph.generate_q(axis, qspace)
Generate a set of q points
input : axis == '001'
equidistant points on z-axis of conventional unit cell
axis == '011'
equidistant points on 011 axis
axis == '111'
equidistant points on 111 axis
axis == 'mp'
Monkhorst-Pack grid
qspace : spacings between q(i+1) and q(i)
return :
qlist = list of qpoints
ph.DOS(qspace, wspace)
Calculate DOS
input : qspace - interspacings between q points
wspace - frequency spacings for binning
return : DOS - Density of states
freq - list of frquencies
np.sum(DOS*freq[1:]) = 1
ph.plot(axis, dspace, espace)
Function to generate publication quality plots
input : axis == 'DOS'
plot DOS
axis == '001'
plot dispersion along 001
axis == '011'
plot dispersion along 011
axis == '111'
plot dispersion along 111