Corundum Lewis J, Schwarzenbach D, Flack H D Acta Crystallographica A38 (1982) 733-739 Electric field gradients and charge density in corundum alpha-Al2O3 _database_code_amcsd 0009325 4.7602 4.7602 12.9933 90 90 120 R-3c atom x y z U(1,1) U(2,2) U(3,3) U(1,2) U(1,3) U(2,3) Al 0 0 .35216 .00279 .00279 .00296 .001395 0 0 O .30624 0 .25 .00327 .00341 .00365 .001635 .00047 .00094