Chalcogen, Rare earth, Energy gap for indirect transition

• La-O
• Ba-Cu-F-O-Y
• Eu-O
• Gd-O-S
• Co-La-O
• rare earth
• chalcogen
• non-disordered
• lanthanoid
• ternary
• trigonal
• tetragonal
• cubic
• orthorhombic
• hexagonal