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By using silicon in the diamond structure an example, short description on the basic input variables for solid is provided here.
nfinp_scf
:
# # Crystalline silicon in the diamond structure # WF_OPT DAV NTYP 1 NATM 2 TYPE 2 NSPG 227 GMAX 4.00 GMAXP 8.00 KPOINT_MESH 8 8 8 KPOINT_SHIFT OFF OFF OFF WIDTH 0.0002 EDELTA 0.5000D-09 NEG 8 CELL 10.30 10.30 10.30 90.00 90.00 90.00 &ATOMIC_SPECIES Si 28.0900 pot.Si_pbe1 &END &ATOMIC_COORDINATES CRYSTAL 0.000000000000 0.000000000000 0.000000000000 1 1 1 0.250000000000 0.250000000000 0.250000000000 1 1 1 &END
Each input variables and blocks (&[BLOCK_NAME] ... &) are explained below:
WF_OPT DAV
WF_OPT
is used to specify the wave function method. Default is DAV
.
NTYP 1
NTYP
defines the number of atomic species in the system.
NATM 2
NATM
defines the number of atoms in the unit cell.
TYPE 2
TYPE
defines the Bravis lattice 2 is for the face centered cubic. Default is 0 (Simple lattice).
NSPG 227
NSPG
is the space group number. Default is 1. Note not all the space group operations are implemented.
GMAX 4.00
GMAX
is the cutoff wave vector for the plane wave expansion of the wave functions. GMAX**2 corresponds to the cutoff energy in Rydberg.
GMAXP 8.00
GMAXP
is the cutoff wave vector for the plane wave expansion of charge density. GMAXP**2 corresponds to the cutoff energy in Rydberg. When only the normconserving pseudopotentials are used, GMAXP
should be twice as GMAX
and can be omitted.
KPOINT_MESH 8 8 8
KPOINT_MESH
is used to define the k-point mesh for the Brillouin zone sampling.
KPOINT_SHIFT OFF OFF OFF
KPOINT_SHIFT
is used to specify if the k-point is shifted or not. If shifted, the Gamma-point is _not_ included in the k-point set.
WIDTH 0.0002
WIDTH
is the width of the broadening (in Hartree) to approximate the delta function. For systems with a gap, very small positive WIDTH
is used. In such a case, it does not have a physical meaning and is used to determine the Fermi level.
EDELTA 0.5000D-09
EDELTA
is the convergence threshold for the total energy in Hartree per atom for the SCF calculation.
NEG 8
NEG
is the number of states/bands considered in the calculation. STATE does not allow an occupied-state only calculation, and therefore NEG
should be large enough to include occupied states and some unoccupied states.
CELL 10.30 10.30 10.30 90.00 90.00 90.00
CELL
defines the cell parameter a, b, c, \alpha, \beta, and \gamma, where a, b, c, are the lengths (in Bohr) of the 1st, 2nd, and 3rd lattice vectors, respectively, and \alpha, \beta, and \gamma, are the angles (in degree) between 2nd and 3rd, 3rd and 1st, and 1st and 2nd lattice vectors, respectively.
&ATOMIC_SPECIES
Si 28.0900 pot.Si_pbe1
&END
The block &ATOMIC_SPECIES ... &END
is used to define the atomic types. The syntax is similar to the one in Quantum-ESPRESSO.
Syntax:
&ATOMIC_SPECIES ATOMIC_NUMBER(1) ATOMIC_MASS(1) PSEUDOPOTENTIAL_FILE(1) ATOMIC_NUMBER(2) ATOMIC_MASS(2) PSEUDOPOTENTIAL_FILE(2) ... ATOMIC_NUMBER(NTYP) ATOMIC_MASS(NTYP) PSEUDOPOTENTIAL_FILE(NTYP) &ENDor:
&ATOMIC_SPECIES ATOMIC_SYMBOL(1) ATOMIC_MASS(1) PSEUDOPOTENTIAL_FILE(1) ATOMIC_SYMBOL(2) ATOMIC_MASS(2) PSEUDOPOTENTIAL_FILE(2) ... ATOMIC_SYMBOL(NTYP) ATOMIC_MASS(NTYP) PSEUDOPOTENTIAL_FILE(NTYP) &ENDwhere
NTYP
is the number of atomic species.
&ATOMIC_COORDINATES CRYSTAL
0.000000000000 0.000000000000 0.000000000000 1 1 1
0.250000000000 0.250000000000 0.250000000000 1 1 1
&END
The block &ATOMIC_COORDINATES ... &END
is used to define the atomic coordinates in the legacy STATE format.
Syntax:
&ATOMIC_COORDINATES [CRYSTAL|CRYS|CARTESIAN|CART] CPS(1,1) CPS(1,2) CPS(1,3) IWEI(1) IMDTYP(1) ITYP(1) CPS(2,1) CPS(2,2) CPS(2,3) IWEI(2) IMDTYP(2) ITYP(2) ... CPS(NATM,1) CPS(NATM,2) CPS(NATM,3) IWEI(NATM) IMDTYP(NATM) ITYP(NATM) &END
CARTESIAN
/CART
: If set, atomic coordinates are given in the cartesian coordinate
CRYSTAL
/CRYS
: If set, atomic coordinates are given in the crystal coordinate
CPS
: Atomic coordinate in the cartesian (NCORD=1
orCOORD=CARTESIAN
) or in the crystal (NCORD=0
orCOORD=CRYSTAL
) coordinate
IWEI
: number of equivalent atoms under the inversion symmetry (currently inversion symmetry is disabled and alwaysIWEI
is always set to 1).
IMDTYP
:
- 1: Allow to move the ion
- 0: Fix the ion
Default coordinate system is
CARTESIAN
. This is chosen when&ATOMIC_COORDINATES
without argument is used.