C
or
C SD followed by the ESD's in the corresponding parameters on the
C card
or
C SD PROD followed by the ESD's in the 6 cell quadratic products
ITEMS DEMANDED:
C , , and any others of
which are not
implied by the space group symmetry (which must have already
been set up).
ASSUMPTIONS MADE:
As zero is not a plausible value for either a cell side or an angle, any of the 6 values which is read as zero is deduced from the space group symmetry, assuming that it is either fixed or related to one of the values read previously.
DETAILS:
and
are cell sides in real space, normally in Å,
but they need not be. However note that the units must
be compatible with
units on F cards,
on D cards etc.
,
and
are the interaxial angles in degrees.
The C SD PROD form should be used when the cell dimensions have been determined from d-spacing values only (eg program DSLSQ) If a C SD line is given without other data, then it will be filled in in the new CDF after a least squares refinement of the unit cell has been made.
NOTE:
Any change of units from Å may lead to implausible default values e.g. for bond lengths used in slack constraints. It will also have consequences on the extinction parameters.
EXAMPLES:
C 5.4560 5.4560 12.6700 90.0 90.0 120.0
C 5.4560 0 12.6700
C 5.4560, 0, 12.6700
C 5.4560,,12.6700
with hexagonal symmetry, are all equivalent. However,
C 5.456 12.67
would not be; this says a=5.4560 and b=12.6700
ROUTINES WHICH READ THE CARDS:
Routine RECIP calls INPUTC to read the C card and then deduces the real and reciprocal cells and transformations. (Routine SETFC also calls RECIP).