[Wien] Effect of spin-orbit on equilibrium lattice constant

[Fred Nastos]

Dear WIEN users,

Is it well understood how the equilibrium lattice constants
change when spin-orbit interactions are included?  For
example, say I calculate the equilibrium lattice constant
for some crystal without spin-orbit.  Can one say with any
confidence whether the equilibrium lattice with spin-orbit
will be larger/smaller?  Is this discussed anywhere?  Should
I have learned this in class?!

Thanks