cd Utility
Now you need to compile a program ( setpar ) that will help you in determining the parameters to be included in PARAM . This can be done by simply tapying:
make
Now edit the file setpar.in in order to specify the physical dimension of your system (size of the simulation cell, number of atoms, number of electrons, etc.)
IBRAV CELLDM(1) .... CELLDM(6)
ECUT
NSX NAX1 NAX2
NX
Description of the variable in file setpar.in :
IBRAV index of the bravais lattice of the simulation cell.
-----
IBRAV STRUCTURE
1 cubic P (sc)
2 cubic F (fcc)
3 cubic I (bcc)
4 Hexagonal and Trigonal P
5 Trigonal R
6 Tetragonal P (st)
7 Tetragonal I (bct)
8 Orthorhombic P
12 Monoclinic P
14 Triclinic P
CELLDM(1 - 6) dimensions of the simulation cell
------
In particular CELLDM(1) is the first cell edge ( usually referred as "a"),
other CELLDMs depend on the point group of the lattice, see table below :
point group bravais lattice ibrav celldm(2)-celldm(6)
...................................................................
432,<4>3m,m3m sc 1 not used
.....................................................................
23,m3 sc 1 "
.....................................................................
432,<4>3m,m3m fcc 2 "
.....................................................................
23,m3 fcc 2 "
.....................................................................
432,<4>3m,m3m bcc 3 "
.....................................................................
23,m3 bcc 3 "
.....................................................................
622,6mm,
<6>m2,6/mmm hex(p) 4 celldm(3)=c/a
.....................................................................
6,<6>,6/m, hex(p)
32,3m,<3>m trig(p) 4 "
.....................................................................
3,<3> trig(p) 4 "
.....................................................................
32,3m,<3>m trig(r) 5 celldm(4)=cos(aalpha)
.....................................................................
3,<3> trig(r) 5 "
.....................................................................
422,4mm,
<4>2m,4/mmm tetr(p) 6 celldm(3)=c/a
.....................................................................
4,<4>,4/m tetr(p) 6 "
.....................................................................
422,4mm,
<4>2m,4/mmm tetr(i) 7 "
.....................................................................
4,<4>,4/m tetr(i) 7 "
.....................................................................
222,mm2,mmm orth(p) 8 above + celldm(2)=b/a
.....................................................................
2,m,2/m mcln(p) 12 above + celldm(4)=cos(ab)
.....................................................................
1,<1> tcln(p) 14 celldm(2)= b/a
celldm(3)= c/a
celldm(4)= cos(bc)
celldm(5)= cos(ac)
celldm(6)= cos(ab)
ECUT Energy cut-off ( ! in Rydberg ), for the reciprocal space representation.
----
NSX maximum number of atomic species in the simulation, in this version
--- it could be only 1 or 2.
NAX1 maximum number of atoms for species 1 (at least 1)
----
NAX2 maximum number of atoms for species 2 (it could be 0)
----
NX Maximum number of electronic energy levels
--
After you have edited and modified setpar.in according to your needs, run the command :
setpar < setpar.in
setpar, on the basis of your physical dimensions, will determine the array dimensions for the simulation program. Now, you are left to copy the values of parameters that you read on the standard output into the PARAM file, where specified as a comment in the file itself.
N.B. : Notice that the file PARAM contians additional information that need NOT be changed.