[Open access]

Acta Cryst. (2013). E69, i63-i64
[ doi:10.1107/S1600536813025154 ]

Redetermination of tamarugite, NaAl(SO4)2·6H2O

K. Mereiter

Key indicators

checkCIF/PLATON results

No syntax errors found

Alert level C PLAT222_ALERT_3_C Large Non-Solvent H Uiso(max)/Uiso(min) .. 5.0 Ratio
Author Response: H14a is the only hydrogen atom involved in a stongly bent hydrogen bond O14w---H14a...O5(viii) = 128.8 deg. This may explain its comparatively large U(iso) of 0.18(2).
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         13      
PLAT975_ALERT_2_C Positive Residual Density at 0.68A from O14W   .       0.41 eA-3 

Alert level G PLAT005_ALERT_5_G No _iucr_refine_instructions_details in the CIF ? Do ! PLAT007_ALERT_5_G Note: Number of Unrefined Donor-H Atoms ........ 12
Author Response: All hydrogen atoms were refined as parts of rigid water molecules with idealized O-H = 0.80 Angstroem and H-O-H = 108 deg using AFIX 6 of program SHELXL. Thus each H2O molecule is refined in x,y,z of the pivot atom oxygen and in orientation (3 Eulerian angles). The presently available SHELXL-based software does not provide suitable e.s.d.s calculation for such refinement procedure and the checkCIF regards them as unrefined.
PLAT128_ALERT_4_G Note: Alternate Setting of Space-group P21/c   .      P21/a      
Author Response: Space group P21/a, structure setting, and most atom names were taken from the earlier structure determmination of Robinson & Fang (1969), Amer. Mineral. 54, 19-30. Their unit cell appears to conform with earlier published crystal morphology.
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Al      (III)         2.93      
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600          5      

0 ALERT level A = Most likely a serious problem - resolve or explain 0 ALERT level B = A potentially serious problem, consider carefully 3 ALERT level C = Check. Ensure it is not caused by an omission or oversight 5 ALERT level G = General information/check it is not something unexpected 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 1 ALERT type 2 Indicator that the structure model may be wrong or deficient 2 ALERT type 3 Indicator that the structure quality may be low 2 ALERT type 4 Improvement, methodology, query or suggestion 3 ALERT type 5 Informative message, check

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