
# Ferroelectric phase of LiNbO3 (R3c symmetry).
# Perdew-Burke-Ernzerhof GGA functional for exchange and correlation.
# 4 x 4 x 4 Monkhorst-Pack grid.

# In siesta:
# Basis set optimized in the paraelectric phase of LiNbO3.
# 400 Ry + 7 internal points.
# Configuration for Li pseudopotential: 2s1, 2p0, 3d0, 4f0
# Configuration for Nb pseudopotential: 4s2, 4p6, 4d4, 4f0
# Configuration for O pseudopotential:  2s2, 2p4, 3d0, 4f0


# In abinit ( M. Veithen and Ph. Ghosez, Phys. Rev. B, 65, 214302 (2002) ).
# 35 Ha if cutoff
# Configuration for Li pseudopotential: 1s, 2s
# Configuration for Nb pseudopotential: 4s, 4p, 4d, 5s
# Configuration for  O pseudopotential: 2s, 2p

                        Siesta           Abinit         Experiment    Siesta-2
                     (Basis set 4)                                (Basis set 7)
 a'(Ang)                5.553834          5.513           5.499       5.564576
 alpha'(degrees)        55.6141           56.270          55.857      55.6158
 Delta Li               0.0300            0.0318          0.0329      0.0296
 Delta O1               0.0106            0.00973         0.00947
 Delta O2               0.0312            0.0382          0.0383
 Delta O3               0.0194            0.0199          0.0192      0.0200
                     -5970.009421                                  -5969.978510

# Cartesian coordinates in Ang of the 10 atoms in the rhombohedric unit cell.
# The cartesian coordinates from Abinit are reported in page 70
# of the Diploma work of Marek Veithen, available at
# http://www.phythema.ulg.ac.be/Download/download.php
# For the (x,y) coordinates of Oxygen, the differences are
# obtained between symmetry equivalent atoms.
# The reference in the differences are the Abinit positions
 
                 Siesta                       Abinit            Difference
Nb1         0.000   0.000   0.000      0.000  0.000  0.000   0.000  0.000  0.000
Nb2         0.000   0.000   7.019      0.000  0.000  6.867   0.000  0.000 -0.152
Li1         0.000   0.000   3.931      0.000  0.000  3.918   0.000  0.000 -0.013
Li2         0.000   0.000  10.950      0.000  0.000 10.785   0.000  0.000 -0.165
O1         -0.674  -1.543   7.916     -1.526 -0.650  7.752   0.017  0.024 -0.164
O2         -0.999   1.356   7.916      1.326 -0.997  7.752  -0.030  0.002 -0.164
O3          1.674   0.187   7.916      0.200  1.646  7.752  -0.028  0.013 -0.164
O4          0.917  -1.308   5.576     -1.267  0.895  5.463   0.041 -0.022 -0.113
O5         -1.591  -0.140   5.576     -0.142 -1.545  5.463  -0.002  0.046 -0.113
O6          0.675   1.448   5.576      1.409  0.650  5.463  -0.039 -0.025 -0.113

