Table 18.

Reduction from 4 to 2

Space group of unstrained crystal, order 4 per lattice point		If stressed so that z ∥ X, Y, or Z		Space group of strained crystal. order 2 per lattice point
		Coordinates referred to axes of unstrained crystal
No.	Symbol	1st Subset	2d Subset	No.	Symbol
75	P4	(x,y, z)	($\overline{y}$, x, z)	3	P2
		($\overline{x}$, $\overline{y}$, z)	(y, $\overline{x}$, z)
76	P41	(x, y, z)	($\overline{y}$, x, ¼+z)	4	P21
		($\overline{x}$,y, ½+z)	(y, $\overline{x}$, ¾+z)
77	P42	(x, y, z)	($\overline{y}$, x, ½+z)	3	P2
		(x, y, z)	(y, $\overline{x}$, ½+z)
78	P43	(x, y, z)	($\overline{y}$, x, ¾+z)	4	P21
		(x, $\overline{y}$, ½+z)	(y, $\overline{x}$, ¼+2)
79	14	(x, y, z)	($\overline{y}$, x, z)	5	C2
		($\overline{x}$, $\overline{y}$,, z)	(y, $\overline{x}$, z)
80	141	(x, y, z)	($\overline{y}$, ½+x, ¼+z)	5	C2
		($\overline{x}$, $\overline{y}$, z)	(y, ½-x, ¼+z)