Electric Quadrupole Moment of a Hydrogenlike Ion in $s$ and $p_{1/2}$   States
  Relativistic formulas for the electric quadrupole moment of a hydrogenlike atom, induced by the hyperfine interaction, are derived for $ns_{1/2}$ and $np_{1/2}$ states. Both the magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The formulas are valid for ions with arbitrary nuclear charge and spin. The induced quadrupole moment is compared with the nuclear quadrupole moment for a wide range of hydrogenlike ions. 
Y.S. Kozhedub and V.M. Shabaev