The magnetic and electronic properties of La(4)Ni(3)O(8) are investigated by performing the full-potential linearized augmented plane wave method. The C-type antiferromagnetic spin ordering is preferred and a molecular correlated insulating state with high-spin Ni ions is found. Our results have proved that this insulating state is caused by a correlation effect and the strong interlayer interaction. Such strong interlayer coupling results from the high-spin occupation of Ni ions.
