272 
PHYSICS: L. W. MCKEEHAN 
Proc. N. a. S. 
Comparing the pattern obtained for Be with that obtained for BeO it was 
found that the first three Hnes in the former and possibly also the fourth 
were attributable to the oxide and its principal impurity. A brief search 
by graphical methods showed that the fundamental space lattice was 
hexagonal, and that the fourth line of pattern might be retained . A more 
exact analysis gives the results presented in Table II, and shows that the 
diffracting points form two symmetrically interpenetrating hexagonal lat- 
tices, each with the axial ratio c/a = 1.58 and with a = 2.283 X 10~^cm. 
No lines are left unaccounted for this structure, which is consistent with 
the hexagonal structure {c/a = 1.5802) determined by optical methods. 
Assuming that one atom is associated with each lattice point, and taking 
N and w as given above, this gives a computed density 1.827 gm./cm^., or 
about one per cent less than the best previous values. The relative po- 
sitions of the two component space lattices along the hexagonal axis are 
not determined with any accuracy, the intensities being very roughly es- 
timated and not particularly significant. 
Comparing the proposed structure for Be with those already reported for 
elements in the same column of the periodic table, it is clear that it belongs 
rather with Mg, Zn, and Cd than with Ca, Sr, and Ba, the first three being 
hexagonal, all with c/a greater than 1.58 and increasing with the atomic 
TABLE I— Be 
ESTIMATED 
MEASURED 
COMPUTED 
ATTRIBUTED 
computed' 
INTENSITY 
2re IN CM. 
LOG (lOM) 
TOl 
LOG (108a) 
2 
4.69 
0.4911 
X3 
6 
6.60 
0.3437 
BeO 
1 
6.97 
0.3201 
BeO 
4 
7.44 
0.2921 
(10.0) 
0.3546 
2 
8.05 
0.2583 
(00.2) 
0.3607 
10 
8.37 
0.2416 
(10.1) 
0.3611 
2 
11.02 
0 . 1244 
(10.2) 
0.3587 
4 
12.89 
0.0583 
(11.0) 
0.3593 
2 
14.44 
0.0108 
(10.3) 
0.3576 
15.55 
5 
5 
18.33 
1.9801 
.9128 
(20.0) 
(11.2) 
(20.1) 
(00.4) 
(20.2) 
(10.4) 
Mean 
Result a = 
0.3593 
0.3572 
0.3586 
2.283 X 10" 
1 All planes theoretically capable of reflection within the range of the tabulated values 
of 2r0 are included. 
2 Computed for c/a = 1.58. 
^ X = impurity in BeO. 
* Diffuse band not resolved. The theoretical range in 2r6 is only 0.58 cm. 
^ Not observed with certainty. 
