Answering your question of NiO with a P lattice; If you take a P structure with 4 Ni and 4 O then you can flip two Ni atoms and you have an antiferro in the 100 direction, which is not the one that you sent in the figure In my earlier message you can see the antiferro ordering in the 111. Both of these structures are frustrated, that is, you cannot put an antiferromagnetic ordering in which the nearest Ni atoms are always antiparallel.
============================================ First, we can create the structure of Cr with 2 ways: 1- with one atom and bcc lattice (0,0,0) or 2- with two atoms and P lattice (0,0,0) and (.5,.5,.5) But the second way allows us to do the antiferromagnetic calculation by flipping the spins of one atom. Second, the same thing, normally, for the Ni element. We can produce the structure with 2 ways: 1- with one atom and fcc lattice (0,0,0) or 2- with four atoms and P lattice (0,0,0) (1/2,1/2,0) (0,1/2,1/2) (1/2,0,1/2) Here we can flip the spins of the two atoms of Ni to do the antiferromagnetic calculation. Third, i want to do the same thing with the NaCl structure (NiO) . I have to get two atoms of Ni at least to reproduce the same crystal structure. And starting with this structure i will determine the equilibrium parameters. the question still how to reproduce the NaCl structure with two or four atoms of Ni so we can do antiferromagnetic calculation with this structure. -------------------------------------------- *** -- Mr: A.Reggad Laboratoire de Génie Physique Université Ibn Khaldoun - Tiaret Algerie
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