ABINIT Discussion Forums

hello evrybody,
im a new user of ABINIT,and i have some problems in input file of oxygene atom,and i find some variables mysteries,so can you help me please??
think you,
best regard

Your question is too vague. Have you done all the basic tutorials, at least 1-4?

yes i did sir
thats my Input file for singl oxygen atom:
#-_-_-_-_-_-_-_ oxygen atom -_-_-_-_-_-_-_-_-_
diemac 1.5d0
diemix 0.5d0
ecut 20
iscf 2
ixc 10
kptopt 0
kpt 0 0 0
natom 1
nkpt 1
nline 4
nstep 20
nsym 1
ntypat 1
prtvol 10

rprim 1 0 0 0 1 0 0 0 1
symrel 1 0 0 0 1 0 0 0 1
tnons 24*0
toldfe 1.0d-14

typat 1
wtk 1
znucl 8
xred 0 0 0
occopt 1
#_-_-_-_end of file_-_-_-_-_-_-_-_-

I don't see an acell in your input--that means you are using the default acell, which is 1 bohr, so your box is only 1 bohr per side. This is obviously too small. Try acell 3*15. Next, with occopt 1, the levels will be filled as for a semiconductor (forced double occupancy) which is not what you want for oxygen. Probably you should use occopt 0 and set the occupations by hand. Third, oxygen is an open shell atom with a magnetic ground state so you need to allow for spin degrees of freedom, through nsppol 2 or nspinor 2. nspinor 2 is probably easier to use in conjunction with occopt 0. Fourth, don't be surprised if, even done properly, you don't get good agreement on a single open-shell atom with experimental levels. To do that you would probably have to use a real space code like GAMESS and a better method for correlation like CASSCF. If your real interest is in atoms, abinit probably isn't the best choice of software. If your real interest is in solids, you will probably find it easier to get up to speed on a simple solid (like silicon, everything works on silicon ;) .

hello again sir
I follow your advices and I have corrected my input file, but it does not work.
can I have some help from you, sir, this is my new file
#-_-_-_-_-__- o atom in a big box-_-_-_-_-_-_-_-_-_-_-

nsppol 2
occopt 2
nband 1 1
occ 5.0 3.0

spinat 0.0 0.0 1.0

#Definition of the unit cell
acell 10 10 10

#Definition of the atom types
ntypat 1
znucl 8


#Definition of the atoms
natom 1
typat 1
xcart

0.0 0.0 0.0

#Definition of the planewave basis set
ecut 10.0
#Definition of the k-point grid
kptopt 0
nkpt 1

#Definition of the SCF procedure
nstep 20
toldfe 1.0d-10

diemac 2.0

optforces 1
#-_-_-_-_end of file-_-_-_-_-_
thanks for advance sir