Acta Cryst. (2005). E61, i76-i78  [ doi:10.1107/S1600536805011049 ]

Dicerium disilicate, Ce₂[Si₂O₇]

B. Deng and J. A. Ibers

Online 23 April 2005

Key indicators

• Single-crystal X-ray study
• T = 153 K
• Mean (i-O) = 0.006 Å
• R factor = 0.024
• wR factor = 0.055
• Data-to-parameter ratio = 13.6

checkCIF/PLATON results

No syntax errors found




Alert level C
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.522
           From the CIF: _refine_ls_abs_structure_Flack_su    0.019
PLAT033_ALERT_2_C Flack Parameter Value Deviates from Zero .......       0.52       
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.01       

Alert level G
FORMU01_ALERT_1_G  There is a discrepancy between the atom counts in the
            _chemical_formula_sum and _chemical_formula_moiety. This is
            usually due to the moiety formula being in the wrong format.
            Atom count from _chemical_formula_sum:   Ce4 O14 Si4
            Atom count from _chemical_formula_moiety:
REFLT03_ALERT_1_G ALERT: Expected hkl max differ from CIF values
           From the CIF: _diffrn_reflns_theta_max           28.93
           From the CIF: _reflns_number_total               2729
           From the CIF: _diffrn_reflns_limit_ max hkl    9.    9.   31.
           From the CIF: _diffrn_reflns_limit_ min hkl   -9.   -8.  -31.
           TEST1: Expected hkl limits for theta max
           Calculated maximum hkl    9.    9.   33.
           Calculated minimum hkl   -9.   -9.  -33.
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           28.93
           From the CIF: _reflns_number_total               2729
           Count of symmetry unique reflns         1545
           Completeness (_total/calc)            176.63%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1184
           Fraction of Friedel pairs measured     0.766
           Are heavy atom types Z>Si present        yes

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

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