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273 bytes added ,  12:38, 19 December 2014
Line 145: Line 145:  
  PARAMETERS OF THE REDUCED CELL (ANGSTROEM & DEGREES)
 
  PARAMETERS OF THE REDUCED CELL (ANGSTROEM & DEGREES)
 
     34.71    84.72    213.67    90.35    90.27    90.06
 
     34.71    84.72    213.67    90.35    90.27    90.06
This clearly indicates that the third axis above the table (with 1/length=34.71) actually should be twice that size. If this happens, the histogram of indexed spots often has two equally-large subtrees:
+
Do you see the half-integer difference vectors in the last column? This clearly indicates that the third axis above the table (with 1/length=34.71) actually should be twice that size. If this happens, the histogram of indexed spots often has two equally-large subtrees:
 
  SUBTREE    POPULATION
 
  SUBTREE    POPULATION
 
   
 
   
Line 154: Line 154:  
     5            6
 
     5            6
   −
Remedy: take the reduced cell below the table, but double the 34.71, and stick it into the line
+
Remedy: take the reduced cell (as found below the table), but double the 34.71, and stick it into the line
 
  UNIT_CELL_CONSTANTS=69.42    84.72    213.67    90.35    90.27    90.06  
 
  UNIT_CELL_CONSTANTS=69.42    84.72    213.67    90.35    90.27    90.06  
To make XDS use that line, specify  
+
in XDS.INP. To make XDS actually ''use'' that line, specify  
 
  SPACE_GROUP_NUMBER=1
 
  SPACE_GROUP_NUMBER=1
 
and leave the space group determination for later.
 
and leave the space group determination for later.
Line 162: Line 162:  
Alternatively, try several well-separated SPOT_RANGEs instead of 1. For example, instead of
 
Alternatively, try several well-separated SPOT_RANGEs instead of 1. For example, instead of
 
  SPOT_RANGE=1 900
 
  SPOT_RANGE=1 900
try
+
try e.g.
 
  SPOT_RANGE=1 100
 
  SPOT_RANGE=1 100
 
  SPOT_RANGE=801 900
 
  SPOT_RANGE=801 900
In most cases, this makes IDXREF pick up the correct cell.
+
In the cases where I've tried this, this splitting of SPOT_RANGE into several wedges always resulted in IDXREF picking up the correct cell.  
   −
I have seen this working well in many cases of too short cell parameters.
+
The reason for the indexing failure in these cases seems to be the fact that the crystal changed its orientation within the SPOT_RANGE by more than ~ 0.1°.
    
=== IDXREF prints !!! WARNING !!! message ===
 
=== IDXREF prints !!! WARNING !!! message ===
2,443

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