Chalcogen, Lanthanoid, Rare earth, Energy gap for indirect transition

• Eu-O
• La-O
• Gd-O-S
• Co-La-O
• Se-Sm
• rare earth
• chalcogen
• lanthanoid
• non-disordered
• oxide
• trigonal
• tetragonal
• cubic
• orthorhombic
• monoclinic