ABINIT Discussion Forums

Dear All,

I want to calculate silicene (graphene like silicon). I used xangst and conventional cell, thus, I used acell : 3*1 and rprim is 100,010, 001 . many "NaN" appear including total energy. Hopefully someone can show me source of the problem. thank you very much in advance. Here is my input file :

# Crystalline silicon : computation of the total energy
#

#Definition of the unit cell
acell 3*1 angstrom # This is equivalent to 10.18 10.18 10.18
rprim 1.0 0.0 0.0 # In lessons 1 and 2, these primitive vectors
0.0 1.0 0.0 # (to be scaled by acell) were 1 0 0 0 1 0 0 0 1
0.0 0.0 1.0 # that is, the default.

chkprim 0
ixc 11
#Definition of the atom types
ntypat 1 # There is only one type of atom
znucl 14 # The keyword "znucl" refers to the atomic number of the
# possible type(s) of atom. The pseudopotential(s)
# mentioned in the "files" file must correspond
# to the type(s) of atom. Here, the only type is Silicon.


#Definition of the atoms
natom 106 # There are
typat 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1



xangst
-11.400000 -13.821765 0.000000
-10.260000 -11.847228 0.000000
-7.980000 -11.847228 0.000000
-6.840000 -13.821765 0.000000
-4.560000 -13.821765 0.000000
-3.420000 -11.847228 0.000000
-1.140000 -11.847228 0.000000
0.000000 -13.821765 0.000000
2.280000 -13.821765 0.000000
3.420000 -11.847228 0.000000
5.700000 -11.847228 0.000000
6.840000 -13.821765 0.000000
10.260000 -11.847228 0.000000
-13.680000 -9.872690 0.000000
-11.400000 -9.872690 0.000000
-10.260000 -7.898152 0.000000
-7.980000 -7.898152 0.000000
-6.840000 -9.872690 0.000000
-4.560000 -9.872690 0.000000
-3.420000 -7.898152 0.000000
-1.140000 -7.898152 0.000000
0.000000 -9.872690 0.000000
2.280000 -9.872690 0.000000
3.420000 -7.898152 0.000000
5.700000 -7.898152 0.000000
6.840000 -9.872690 0.000000
9.120000 -9.872690 0.000000
10.260000 -7.898152 0.000000
12.540000 -7.898152 0.000000
-13.680000 -5.923614 0.000000
-11.400000 -5.923614 0.000000
-10.260000 -3.949076 0.000000
-7.980000 -3.949076 0.000000
-6.840000 -5.923614 0.000000
-4.560000 -5.923614 0.000000
-3.420000 -3.949076 0.000000
-1.140000 -3.949076 0.000000
0.000000 -5.923614 0.000000
2.280000 -5.923614 0.000000
3.420000 -3.949076 0.000000
5.700000 -3.949076 0.000000
6.840000 -5.923614 0.000000
9.120000 -5.923614 0.000000
10.260000 -3.949076 0.000000
12.540000 -3.949076 0.000000
-13.680000 -1.974538 0.000000
-11.400000 -1.974538 0.000000
-10.260000 0.000000 0.000000
-7.980000 0.000000 0.000000
-6.840000 -1.974538 0.000000
-4.560000 -1.974538 0.000000
-3.420000 0.000000 0.000000
-1.140000 0.000000 0.000000
0.000000 -1.974538 0.000000
2.280000 -1.974538 0.000000
3.420000 0.000000 0.000000
5.700000 0.000000 0.000000
6.840000 -1.974538 0.000000
9.120000 -1.974538 0.000000
10.260000 0.000000 0.000000
12.540000 0.000000 0.000000
-13.680000 1.974538 0.000000
-11.400000 1.974538 0.000000
-10.260000 3.949076 0.000000
-7.980000 3.949076 0.000000
-6.840000 1.974538 0.000000
-4.560000 1.974538 0.000000
-3.420000 3.949076 0.000000
-1.140000 3.949076 0.000000
0.000000 1.974538 0.000000
2.280000 1.974538 0.000000
3.420000 3.949076 0.000000
5.700000 3.949076 0.000000
6.840000 1.974538 0.000000
9.120000 1.974538 0.000000
10.260000 3.949076 0.000000
12.540000 3.949076 0.000000
-13.680000 5.923614 0.000000
-11.400000 5.923614 0.000000
-10.260000 7.898152 0.000000
-7.980000 7.898152 0.000000
-6.840000 5.923614 0.000000
-4.560000 5.923614 0.000000
-3.420000 7.898152 0.000000
-1.140000 7.898152 0.000000
0.000000 5.923614 0.000000
2.280000 5.923614 0.000000
3.420000 7.898152 0.000000
5.700000 7.898152 0.000000
6.840000 5.923614 0.000000
9.120000 5.923614 0.000000
10.260000 7.898152 0.000000
12.540000 7.898152 0.000000
-11.400000 9.872690 0.000000
-7.980000 11.847228 0.000000
-6.840000 9.872690 0.000000
-4.560000 9.872690 0.000000
-3.420000 11.847228 0.000000
-1.140000 11.847228 0.000000
0.000000 9.872690 0.000000
2.280000 9.872690 0.000000
3.420000 11.847228 0.000000
5.700000 11.847228 0.000000
6.840000 9.872690 0.000000
9.120000 9.872690 0.000000
10.260000 11.847228 0.00000






#Definition of the planewave basis set
ecut 12.0 # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
kptopt 1 # Option for the automatic generation of k points, taking
# into account the symmetry
ngkpt 2 2 2 # This is a 2x2x2 grid based on the primitive vectors
nshiftk 1 # of the reciprocal space (that form a BCC lattice !),
# repeated four times, with different shifts :
shiftk 0.0 0.0 0.0

# In cartesian coordinates, this grid is simple cubic, and
# actually corresponds to the
# so-called 4x4x4 Monkhorst-Pack grid

#Definition of the SCF procedure
nstep 10 # Maximal number of SCF cycles
toldfe 1.0d-6 # Will stop when, twice in a row, the difference
# between two consecutive evaluations of total energy
# differ by less than toldfe (in Hartree)
# This value is way too large for most realistic studies of materials
diemac 12.0 # Although this is not

Hello,

Acell of 1 angstrom and rprim = 100;010;001 gives you a cell of 1 A^3. This is much too small to fit 106 atoms. You should try with a larger cell. With your xangst it should be something like:

acell 3*1 angstrom
rprim 27.36 0.0 0.0 #
0.0 27.643531 0.0 #
0.0 0.0 5.0 # you can change this dimention and test its effect on the energy

You can use Xcrysden to check if there is no problem with your cell.

Julia

thank you Julia

I thought that rprim is not only multiplied by acel but also angst to produce the real size of cell.