checkCIF procedure

PROC-NAME: CELLV02 Type_1

PURPOSE: To check that the _cell_volume su matches _cell_length_ and _cell_angle_ su values.

PROCEDURE: (Ref: Giacovazzo Fundamentals of Crystallography p.122)

CALCULATE

CSA = COSINE [ _cell_angle_alpha ]
CSB = COSINE [ _cell_angle_beta ]
CSG = COSINE [ _cell_angle_gamma ]

SA = SINE [ _cell_angle_alpha ]
SB = SINE [ _cell_angle_beta ]
SG = SINE [ _cell_angle_gamma ]

A1 = (su of a)/_cell_length_a
A2 = (su of b)/_cell_length_b
A3 = (su of c)/_cell_length_c

B1 = SA*(CSA-CSB*CSG)*(su of alpha)
B2 = SB*(CSB-CSA*CSG)*(su of beta)
B3 = SG*(CSG-CSA*CSB)*(su of gamma)

CV = [ ( _cell_length_a * _cell_length_b * _cell_length_c )**4 / (_cell_volume)**2 ]

SUVOL = SQRT {
(_cell_volume)**2 * (A1**2 + A2**2 + A3**2)
+ CV*(B1**2 + B2**2 +B3**2)}

DSUV = |{su of cell volume} - SUVOL |

TEST

IF DSUV > 8 issue ALERT A
   "Alert A The supplied cell volume s.u. differs from that calculated from the cell parameter s.u.'s by > 8"
DSUV > 4 issue ALERT B
   "Alert B The supplied cell volume s.u. differs from that calculated from the cell parameter s.u.'s by > 4"
DSUV > 2 issue ALERT C
   "Alert C The supplied cell volume s.u. differs from that calculated from the cell parameter s.u.'s by > 2"

There is a discrepancy between the standard uncertainty (s.u.) for the unit cell volume given in the CIF and that calculated from the s.u.s of the unit cell dimensions given in the CIF. Check the volume and cell dimension s.u.s for typographical errors (rule of '19' applies).