What is the Catholic understanding of omnipotence?

Castiel wanted to ask this question from a biblical basis: > Can God kill himself ? I mean, if he can kill himself, he isn't > immortal and if he can't, he have not unlimited power... The question here is, what is the Catholic understanding of omnipotence? How do Catholics address the apparent contradiction that God cannot be omnipotent if he cannot kill himself and he cannot be immortal if he can kill himself?