  In the sl\_n case, A. Berenstein and A. Zelevinsky studied the
Sch\"{u}tzenberger involution in terms of Lusztig's canonical basis, [3]. We
generalize their construction and formulas for any semisimple Lie algebra. We
use for this the geometric lifting of the canonical basis, on which an analogue
of the Sch\"{u}tzenberger involution can be given. As an application, we
construct semitoric degenerations of Richardson varieties, following a method
of P. Caldero, [6]
