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 at 1000C after Cameron et al. (1973) with O3-O3-O3 angle = 168.5 and model oxygen radius = 1.330 _database_code_amcsd 0003479 9.876 9.170 5.294 90 109.0 90 C2/c atom x y z Mg 0 11/12 1/4 Ca 0 .25 1/4 Si .3082 1/12 .2709 O1 .1337 1/12 .1647 O2 .3663 .25 .3353 O3 .3663 .0145 .0419