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Re: Unit cells

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Dear fellow re-indexers,

To re-index in the head, figure out how the vectors of the new cell (a', b', c')
relate to the original cell (a,b,c).

>    a=118.806  b=126.818 c=85.610 alpha=90. beta=104.166  gamma=90.
>    a=128.193  b=127.106 c=85.513 alpha=90. beta=115.994  gamma=90.

When transforming from one cell to another, keep the directions in mind
so that the signs work out right (beta is the angle between (+) a and (+) c ).

a'= -(a + c) : (-) new a is the vector sum of old a and c
b' = -b  : so the axes are in the same relative hand
c '= c

Since the indices transform in the same way as the unit cell vectors,
the new indices (h', k', l') are related to the original ones (h, k, l)

h' = -(h + l)
k' = -k
l' = l


Lisa Edberg (205)934-1611 FAX:(205)934-0480
Center for Macromol. Cryst., Univ. Alabama-Birmingham