Wi/ckoff — Crystal Structure of Magnesium Oxide. 1-13 



(*) Mg: f f f, f f f, Iff, Iff, i i f, lit, i i f, i i t, 

 i f I, i f i, i f i, i t i, f i i, f * i, f * *, iih 



iih %ih iih iih %%h i%h ^ih iih 



ST 8 171 :5 5± ±AA XAS A3JL X±± 5.18. 



"S"8""8?8"S"S5 88 8? 8 8 85 88 "S"? 8"5"8?'8 8S? 8 8 8' 



^ • "§■ 8" "85 ■§"■§■¥) # 8" '8 5 ¥ # 8" 5 a S" 8"5 8" F "8 5 "S" 8 '§'5 8" "S" "g"? 



"8 "8 "S"? "8 f "g'J "8" 8" ¥5 "S" f E"5 "8 i 8 > # "S" "S"? "g" "S" 8"? "8 ¥ "S"5 



I" "i" "§"5 ¥ 8" "S"? ¥ ■§" ¥5 ¥ ¥ ¥5 ¥ ¥ ¥5 ¥ ¥ ¥5 ¥ ¥ ¥5 ¥ ¥ ¥5 



¥ ¥ ¥5 8 ¥ ¥5 8 ¥ ¥5 ¥ ¥ 8 5 ¥ ¥ ¥5 ¥ 8 ¥5 ¥ ¥ ¥5 8" ¥ ¥• 



This arrangement is a special case of the space group 



O ^ 



(J) Mg: u u w, ?^+i, u-^\, w, 1^+1 u, 'a-\-^\ v, +1 u-\-^; 



IV II 11', tc-\-^, i—^iy ^f'i ?^+T, ^^ ^—^c, ^^ i — ^^ i—^f, 



u u n; ^ — u, u-\-^, u\ \—'U, n, ^—u; u, w-f-^, ^—ii\ 



u u u\ ^~u, \ — it, n] ^ — i(, u, i(-{-^', u, \ — ii., ^^+-v: • 



%i u ii\ \—n, \ — ^<^, u\ \~u, w, \ — u\ u, ^—u, \ — u-, 



u uii\ \—u, "+i, ?s ¥~'^^ '^^ ^^+t; '^ ^-^+^5 ^^+i; 



: V vv ; and 31 other positions as with Mg. ti and 

 V can have any values from zero to unity. This arrange- 

 ment can be obtained from either the holohedry or from 

 any of the classes of the hemihedry. 



{k) Mg: to u ic; ic-\-^, u, u-\--t', i— ", i— ?^ i" '"; f— "^^ i" ^^ f— '?^; 

 icu u\ ^<-h|, iL, \-u\ \-u, u^\, ?^+i; f-i^ ?y-fi, t^-ff; 

 XL u u; ^—u, ic, i— w; ?^+i, i — u, u-]-^', t^ + f, i— w, ^^+f ; 



iLuu\ ^—u, II, ■«+i; ?«+i, ?^+i, i— ^'; ^^+f, ^^+^5 i—>'\ 

 w+i, z^+i, ^s ^s "+T5 "+i; f-^^ f-'^ i-^^; i-^s f-^^ f-'<; 

 ?^+T5 i-^^ «; ^^ i-^5 i— ^'; l-^^ «+f^ ^^+1; i— ^', «+f, ^^+f ; 

 1-?^, 7J+I, ?^; ■«, u-^\, \-u\ ^^+f, f-'^ ?^+i; ^^+i, f--^^ ?^+f ; 

 i— ^s i-z^ u\ f(, i-u, i^+i; ^^+f, '^^+f, i-ic, ^(+h '^^+f, f-'^- 



: V V v; and 31 other positions as with Mg. u and v 

 again can have any values from zero to unity. This 

 arrangement can be obtained from any but the tetarto- 

 hedral and tetrahedral classes. 



It would obviously be of considerable advantage to 

 know to which class of crystal symmetry magnesium oxide 

 should be assigned. There is, however, a certain amount 



