QHA package, by Eyvaz Isaev - For Quasi-Harmonic Approximation

Executable files can be compiled using the Compile script:

tetra.x           - to generate vertexes of microtetrahedra
matdyn.x          - to generate phonons for microtetrahedra vertexes
Partial_phonon_DOS.x - to project DOS onto a specified atom and its polarization vector
phonon_dos.x      - to calculate phonon DOS and atom projected phonon DOS. 
  
Ghost_DOS.x       - to remove "NaN" statements (taken as (DOS(i-1)+DOS(i+1))/2) with small
                    (order of 0.5THz) frequency step in integration
	      
Atom_projected_properties.x - to integrate phonon DOS, and atom projected DOS to find out
                    atom-specific contribution to the zero point vibration energy, phonon DOS,
                    vibration energy, specific heat, entropy, internal energy, as well as
                    LO and TA  (g_x,g_y,g_z) components of atom-specific phonon DOS
NB!!! The limitation for the program is the presence of only one frequency gap in the phonon spectrum, 
i.e. the program assumes that there are well separated low-lying "acoustic" modes and optical branches.
Hopefully will be corrected for more complex structures to avoid this limitation.

Debye.x - calculates the Debye temperature
F_QHA.x - Total vibrational energy, the specific heat, entropy and internal energy in  the 
          quasiharmonic  approximation
	  C_v is in units of R, the universal gas constant.  
	  If you like to see C_v or S in  kcal/(mol K)  or J/(mol K) then just multilply  the 4th column 
          by a factor of 2 (in kcal/(mol K)), or 8.31 ( in J/(mol K)), respectively.
	  Presumably one needs to divide C_v to a number of formula units in the unit cell.
Mean_Square_Displacements.x - calculates exactly what is declared (in Ang^2)  


To start phonon calculations one needs the following files:

run_Phonon_DOS.sh - the main script - see the Examples directory for examples
matdyn.init       - to specify the force constants matrix and atomic masses 
ttrinp            - Brillouin zone (tetrahedra) information
                    There are predefined ttrinp files for simple cubic, face centered cubic,
		    body centered cubic, hexagonal, simple tetragonal and simple orthorhombic 
		    lattices. For body centered tetragonal with c/a<1 there are instructions 
		    on how to setup ttrinp file (it is quite easy). Maybe the same "trick" 
		    can be applied for other structures with more complicated Brillouin zone.


