CO molecule example
By using a carbon monoxide (CO) in a small rectangular box as an example, short description on the input variables is provided here.
nfinp_scf:
WF_OPT DAV
NTYP 2
NATM 2
GMAX 5.50
GMAXP 20.00
NSCF 200
WAYMIX 3
KBXMIX 8
MIX_ALPHA 0.8
WIDTH 0.0010
EDELTA 0.1000D-09
NEG 8
CELL 6.00 4.00 4.00 90.00 90.00 90.00
&ATOMIC_SPECIES
C 12.011 pot.C_pbe1
O 15.999 pot.O_pbe1
&END
&ATOMIC_COORDINATES
0.0000 0.0000 0.0000 1 1 1
2.2000 0.0000 0.0000 1 1 2
&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 2
NTYP defines the number of atomic species in the system.
NATM 2
NATM defines the number of atoms in the unit cell.
GMAX 5.50
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 20.00
GMAXP is the cutoff wave vector for the plane wave expansion of charge density. GMAXP**2 corresponds to the cutoff energy in Rydberg.
NSCF 200
NSCF is the maximum number of iteration for the wave function optimization [self-consistent field (SCF)]. Default is 200.
WAYMIX 3
WAYMIX defines the charge-density mixing method. Default is 6 [Blugel].
KBXMIX 8
KBXMIX is the number of SCF steps used for the mixing.
MIX_ALPHA 0.8
MIX_ALPHA is the mixing parameter for the charge density mixing. Default is 0.7.
WIDTH 0.0010
WIDTH is the width of the broadening to approximate the delta function in Hartree. For systems with a gap, very small positive WIDTT is used. In such a case, it does not have a physical meaning and is used to determine the Fermi level.
EDELTA 0.1000D-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 6.00 4.00 4.00 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
C 12.011 pot.C_pbe1
O 15.999 pot.O_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
NTYPis the number of atomic species.
&ATOMIC_COORDINATES
0.0000 0.0000 0.0000 1 1 1
2.2000 0.0000 0.0000 1 1 2
&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=1orCOORD=CARTESIAN) or in the crystal (NCORD=0orCOORD=CRYSTAL) coordinate
IWEI: number of equivalent atoms under the inversion symmetry (currently inversion symmetry is disabled and alwaysIWEIis 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_COORDINATESwithout argument is used.