Erbium Wyckoff R W G Crystal Structures 1 (1963) 7-83 Second edition. Interscience Publishers, New York, New York Sample at T = 43 K Hexagonal closest packed, hcp, structure _database_code_amcsd 0011173 3.550 3.550 5.590 90 90 120 P6_3/mmc atom x y z Er 1/3 2/3 .25