1. Tutorial - Practice #2 -
QnMSG
Yong-Hyun Kim

2. Pwscf – Input file < input file >
calculation: method of calculation
etot_conv_thr: convergence threshold on total energy for ionic minimization
forc_conv_thr: convergence threshold on forces for ionic minimization
ibrav: Bravais-lattice index
celldm(i): Crystallographic constants
nat: number of atoms in the unit cell
ntyp: number of type of atoms in the unit cell
ecutwfc: kinetic energy cutoff (Ry) for wavefunctions
diagonalization: Davidson iterative diagonalization with overlap matrix
CELL_PARAMETERS: Lattice parameter
ATOMIC_SPECIES: types of atom
ATOMIC_POSITION: basis of atom
K_POINTS: the number of k-points
The detail things about Input parameter is in ~/espresso-5.0.1/Doc/INPUT_PW.txt

3. Structure
1. To see structure in input file of Pwscf, first, we have to make xyz file using the program named pw2xyz.pl.
2. Program pw2xyz.pl make the xyz file using the lattice parameter and basis in input file.
- Information related to structure in Input file -
- xyz file -
3. Instruction of pw2xyz.pl program is as follows.
file name of input
size of cell (x, y, z)
4. After using the program pw2xyz.pl, geometry.xyz file is made.
5. To see structure, use xmakemol program and then open the xyz file.

4. Running the Pwscf Method running Pwscf
1. Serial calculation :/opt/espresso-5.0.1/bin/pw.x < input
2. Parallel calculation : qsub run.sh
- run.sh -

5. Cutoff vs Energy
- Si bulk -
- Graphene -
70 Ry
25 Ry

6. K-points vs Energy
- Si bulk -
- Graphene -
k-points = 8
k-points = 4

7. Birch–Murnaghan EOS - eos.in - - Instruction -
1. To get the equilibrium volume, we need the Birch-Murnaghan fitting.
2. To do Birch-Murnaghan fitting, we have to run the program named eos.x.
3. To run the program named eos.x, we need the input file named eos.in.
- eos.in -
- Instruction -
4. After enter the eos.x, some files are generated.
- PARAM.out -
Equilibrium volume
(Bohr3)
Bulk modulus

8. Lattice constant vs Energy
- Si bulk -
- Graphene -
a = Bohr
a =5.47 Å
a = 4.63 Bohr
a =2.45 Å

9. Cohesive energy
- The cohesive energies were calculated as the energy difference between the total energy of the free atoms and the bulk solid as given by the equation below:
Ecoh = Eatom - Esolid
(Unit: eV)
Tota energy of Atom
Total energy of solid
Cohesive energy
Si-bulk
5.43
4.631)
Graphene
9.07
8.802)
1) Kittel, Introduction to solid state physics
2) J. Phys. B: At. Mol. Opt. Phys (1996)