Pyroxene-ideal Thompson R M, Downs R T American Mineralogist 89 (2004) 614-628 Model pyroxenes II: Structural variation as a function of tetrahedral rotation model diopside after Cameron et al. (1973) with O3-O3-O3 angle = 166.4 and model oxygen radius = 1.318 _database_code_amcsd 0003478 9.756 9.067 5.235 90 108.7 90 C2/c atom x y z Mg 0 11/12 1/4 Ca 0 .25 1/4 Si .3082 1/12 .2676 O1 .1335 1/12 .1632 O2 .3665 .25 .3368 O3 .3665 .0172 .0352