Elastic constant of ONL materials for exemple ONL materials '' NLO oxides such as BaB2O4 (BBO), LiB3O5 (LBO), LiNbO3 (NLO), KH2PO4 (KDP), and KTiOPO4 (KTP) " or chalcogenide ABQ (S,Se,Te) for exemple (LiGa(S,Se,Te) or LiIn(S,Se,Te) ....etc