Portlandite
Henderson D M, Gutowsky H S
American Mineralogist 47 (1962) 1231-1251
A nuclear magnetic resonance determination of the hydrogen positions in Ca(OH)2
T = 25 C
_database_code_amcsd 0000117
3.5925 3.5925 4.905 90 90 120 P-3m1
atom   x   y     z
Ca     0   0     0
O    1/3 2/3 .2330
H    1/3 2/3  .418