  We use density functional theory to investigate effects of spin-orbit
coupling and single-stripe-type antiferromagnetic (sAFM) ordering on the
crystal structure and electronic properties of SmFeAsO. The results indicate
that AFM ordering causes the crystal structure transition from tetragonal to
orthorhombic, along with increase in the height of As atoms from Fe layer due
to magnetostriction. It also leads to the opening of partial band gaps, the
emergence of a prominent peak near Fermi energy (EF) in the density of states
(DOS) and a reduction in Fermi surface nesting. The study finds a correlation
between the calculated area under the DOS curve, spanning from EF to the first
peak above it, and the optimal electron-doped concentration required for
inducing superconductivity in SmFeAsO. The findings suggest that spin and
charge density waves can play important roles in the superconducting mechanism
of Fe-based superconductors. Our calculations demonstrate that spin-orbit
coupling reduces electronic correlation.
