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[Enrico <enrico.avenati@yahoo.com>]

Hi,
i tried to get the ground state energy of LaNi2  (like structure Cu2Mg)
spcgrp 227 
PEARSON cF24 
i use the rprim matrix for FCC
I got many  xred (see my input ) but none worked!

ERROR -
  According to the symmetry finder, the unit cell is
  NOT primitive. The multiplicity is  4 .
  The use of non-primitive unit cells is allowed
  only when the input variable chkprim is 0.
  Action : either change your unit cell (rprim or angdeg),
  or set chkprim to 0.

If i use chkprim the calculation stops , geometry not consistent with the
spacegrp! 

INPUT
#UNIT CELL 
LaNi2

acell  3*7.387 Angstr

rprim  0.0  0.5  0.5   # Real space PRIMitive translations
       0.5  0.0  0.5 
       0.5  0.5  0.0

spgroup 227 # without space group the spcgrp is not identified

ntypat 2 # 2 types of atoms

znucl  57 28

natom  6 # atom per cell

typat  1 1 2 2 2 2 # LaNi2

xred

#internatinal table of crystallography origin -3m
#1/8 1/8 1/8 # 8a wyckoff position 
#7/8 3/8 3/8
#1/2 1/2 1/2 # 16d
#1/2 1/4 1/4
#1/4 1/2 1/4
#1/4 1/4 1/2

#internatinal table of crystallography origin -43m
0.0 0.0 0.0 #  
1/4 1/4 1/4
5/8 5/8 5/8
5/8 7/8 7/8
7/8 5/8 7/8
7/8 7/8 5/8

#setting input VASP 
#0.0 0.0 0.0 #  Pearson book notation NOT WORKING
#1/4 1/4 1/4
#5/8 5/8 5/8 # Pearson book
#5/8 1/8 5/8
#1/8 5/8 5/8
#5/8 5/8 1/8

FROM THIS POINT IT SHOULD BE OK, BUT HAVE A 

#RECIPROCAL SPACE INTEGRETION
kptopt 1
ngkpt 2 2 2

nshiftk 4            # shiftk=4 particular efficient for FCC 
shiftk 0.5 0.5 0.5
       0.5 0.0 0.0
       0.0 0.5 0.0
       0.0 0.0 0.5

nband 25
tsmear 0.02
occopt 4

#PLANE WAVES
ecut 20

#SCF PROCEDURE
nstep 50
ixc 1
toldfe 1.0d-7

thank you, hope you could help!