Alkali, Chalcogen, Non-disordered, Energy gap for indirect transition

• Na-O-Si
• Bi-Na-O-W
• Cu-K-S-Sb
• K-Nb-O
• Na-O-Ta
• non-disordered
• alkali
• chalcogen
• ternary
• transitional
• trigonal
• monoclinic
• tetragonal
• orthorhombic
• hexagonal