The ABINIT Users Mailing List ( CLOSED )

["Barrera, G (Gustavo) " <G.Barrera@rl.ac.uk>]

Dear ab init users,

I interested in calculating the elastic constants of Cu and Au (both simple
fcc metals). For that I used the Troullier-Martins pseudopotentials
available on the web, a cutoff of 40 Ry, a grid of 8 x 8 x 8 k points and
the input file given below.
The results for the bulk moduluae I have got (in GPa) are:

                 Cu    Au
My calculation  180   188
Experiment      142   180
Other calc.     144   180

So I am getting a value of B for Cu that is much higher than previous ab
initio calculations.

Any ideas about what am I doing wrong?

Thank you very much


Gustavo Barrera
ISIS, Rutherford Appleton Laboratory

Full input follows:

# Cu  crystal
#

#Definition of occupation numbers
occopt 7
tsmear 0.01

kptopt 1          # Take fully into account the symmetry
ngkpt 8 8 8         # Number of Grid points for K PoinTs generation

ndtset 15                  #   Gives the number of data sets to be treated
#Definition of the unit cell
acell1 3.0 3.0 3.0  angstrom
acell2 3.1 3.1 3.1  angstrom
acell3 3.2 3.2 3.2  angstrom
acell4 3.3 3.3 3.3  angstrom
acell5 3.4 3.4 3.4  angstrom
acell6 3.5 3.5 3.5  angstrom
acell7 3.6 3.6 3.6  angstrom
acell8 3.7 3.7 3.7  angstrom
acell9 3.8 3.8 3.8  angstrom
acell10 3.9 3.9 3.9  angstrom
acell11 4.0 4.0 4.0  angstrom
acell12 4.1 4.1 4.1  angstrom
acell13 4.2 4.2 4.2  angstrom
acell14 4.3 4.3 4.3  angstrom
acell15 4.4 4.4 4.4  angstrom

rprim  0.0  0.5  0.5
       0.5  0.0  0.5
       0.5  0.5  0.0


#Definition of the atom types
ntype 1           # There is only one type of atom
zatnum 29         # The keyword "zatnum" 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 Hydrogen.


#Definition of the atoms
natom 1           # total number of atoms in unit cell
type 1            # They both are of type 1, Cu
xred              # atom positions in REDuced coordinates
   0.0 0.0 0.0    #

#Definition of the planewave basis set
ecut 40.0         # Maximal plane-wave kinetic energy cut-off, in Hartree


#Definition of the SCF procedure
nstep 50          # 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)