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 Levien and Prewitt (1981) with O3-O3-O3 angle = 166.4 and model oxygen radius = 1.319 _database_code_amcsd 0003480 9.760 9.071 5.237 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 .1631 O2 .3664 .25 .3369 O3 .3664 .0172 .0351