Table 7.

Reduction from $\overline{6}m2$ to mm2

Space group of unstrained crystal, order 12 per lattice point		If stressed so that y and z ∥ any two of X, Y, and Z			Space group of strained crystal, order 4 per lattice point
		Coordinates referred to axes of unstrained crystal
No.	Symbol	1st Subset	2d Subset	3d Subset	No.	Symbol
187	P$\overline{6}$m2	(x, y, z)	($\overline{y}$,x-y, z)	(y-x,$\overline{x}$, z)	38	Amm2
		(x,x—y, z)	($\overline{y}$, $\overline{x}$, z)	(y-x,y, z)
		(x, y, $\overline{z}$)	($\overline{y}$,x-y, $\overline{z}$)	(y-x,$\overline{x}$, $\overline{z}$)
		(x,x—y, $\overline{z}$)	($\overline{y}$, $\overline{x}$, $\overline{z}$)	(y-x,y, $\overline{z}$)
188	P$\overline{6}$c2	(x, y, z)	($\overline{y}$,x-y, z)	(y-x,$\overline{x}$, z)	40	Ama2
		(x,x-y,½-z)	(y, $\overline{x}$, ½-z)	(y-x,y,½-z)
		(x, y, ½-z)	($\overline{y}$,x-Y,½-z)	(y-x,$\overline{x}$,½-z)
		(x,x— y, $\overline{z}$)	($\overline{y}$, $\overline{x}$, $\overline{z}$)	(y-x,y, $\overline{z}$)
189	P$\overline{6}$2m	(x, y, z)	($\overline{y}$,x-y, z)	(y-x,$\overline{x}$, z)	38	Amm2
		(x, y-x, z)	(y, x, z)	(x-y, y, z)
		(x, y, $\overline{z}$)	($\overline{y}$,x-y, $\overline{z}$)	(y-x,$\overline{x}$, $\overline{z}$)
		($\overline{x}$,y-x, $\overline{z}$)	(y, x, $\overline{z}$)	(x-y,$\overline{y}$, $\overline{z}$)
190	P$\overline{6}$2e	(x, y, z)	($\overline{y}$, x-y, z)	(y-x,$\overline{x}$, z)	40	Ama2
		($\overline{x}$,y-x,½+z)	(y, x, ½+z)	(x-y, y, ½+z)
		(x, y, ½-z)	($\overline{y}$,x-y, ½-z)	(y-x,$\overline{x}$,½-z)
		(x,y-x, $\overline{z}$)	(y, x, $\overline{z}$)	(x-y,$\overline{y}$, $\overline{z}$)