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Acta Cryst. (2001). E57, i87-i89  [ doi:10.1107/S1600536801015094 ]

Hexagonal YbMnO3 revisited

B. B. Van Aken, A. Meetsma and T. T. M. Palstra

Online 29 September 2001

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Red Alert Alert Level A:



PLAT_211  Alert A ADP of atom  O2     is non-positive-definite .          ?
Author response: ... Our calculations show that although the smallest principal mean square displacement of O2 is very small, 0.0001, it is not zero or negative. Note that oxygen compared with ytterbium has only very few electrons, 8 versus 70. However using isotropic atomic displacement for all oxygen positions, yields a very similar model. All atomic positions stay equal within the error of the refinement. The isotropic a.d.p.'s for the oxygen range between 0.0051(14) and 0.0071(11). 
PLAT_211  Alert A ADP of atom  O4     is non-positive-definite .          ?
Author response: ... Our calculations show that although the smallest principal mean square displacement of O2 is very small, 0.0001, it is not zero or negative. Note that oxygen compared with ytterbium has only very few electrons, 8 versus 70. However using isotropic atomic displacement for all oxygen positions, yields a very similar model. All atomic positions stay equal within the error of the refinement. The isotropic a.d.p.'s for the oxygen range between 0.0051(14) and 0.0071(11). 

Amber Alert Alert Level B:



DIFMN_02  Alert B The minimum difference density is < -0.1*ZMAX*1.00            
          _refine_diff_density_min given =     -7.300                           
          Test value =     -7.000
Author response: ... The differences in final electron density between calculation and observation are well known and appear to be present in most lanthanide manganese oxides. 
PLAT_111  Alert B ADDSYM detects (pseudo) centre of symmetry ...        100 Perc Fit
Author response: ... Attempts to fit the data on a crystal structure with a space group that contains higher symmetry, like P63/mcm, where unsuccessful. A.d.p.'s indicated that the atoms at the mirror plane ought to be split in two on each side of the mirror plane. For instance an inversion symmetry on z //simeq 0.252 forces the two inequivalent Yb positions to have identical values for their z parameter. As the z parameter is free on all P63cm positions and the current refinement separates the z parameters by as much as 0.04, equivalent to 0.25 \%A, it is very unlikely that additional symmetry is missed. 
PLAT_111  Alert B ADDSYM detects (pseudo) centre of symmetry ...        100 Perc Fit
Author response: ... Attempts to fit the data on a crystal structure with a space group that contains higher symmetry, like P63/mcm, where unsuccessful. A.d.p.'s indicated that the atoms at the mirror plane ought to be split in two on each side of the mirror plane. For instance an inversion symmetry on z //simeq 0.252 forces the two inequivalent Yb positions to have identical values for their z parameter. As the z parameter is free on all P63cm positions and the current refinement separates the z parameters by as much as 0.04, equivalent to 0.25 \%A, it is very unlikely that additional symmetry is missed. 

Yellow Alert Alert Level C:



DIFMN_03  Alert C The minimum difference density is < -0.1*ZMAX*0.75            
          The relevant atom site should be identified.                          

General Notes



ABSTM_02  The ratio of expected to reported Tmax/Tmin(RR) is > 2.00             
          Tmin and Tmax reported:      0.059     0.577                          
          Tmin and Tmax expected:      0.011     0.568                          
          RR =      5.193                                                       
          Please check that your absorption correction is appropriate.          

REFLT_03                                                                        
         From the CIF: _diffrn_reflns_theta_max           39.90                 
         From the CIF: _reflns_number_total                835                  
         Count of symmetry unique reflns          434                           
         Completeness (_total/calc)            192.40%                          
         TEST3: Check Friedels for noncentro structure                          
         Estimate of Friedel pairs measured       401                           
         Fraction of Friedel pairs measured     0.924                           
         Are heavy atom types Z>Si present          yes                         
          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.          


 2 Alert Level A = Potentially serious problem

 3 Alert Level B = Potential problem

 1 Alert Level C = Please check

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