Database of Disordered Zeolite Structures
 
Intergrowth Family IM-18
Periodic Building Unit
 
  Periodic Building Unit (PerBU): Layer of isolated zig-zag chains  
  Layer symmetry P m m (2)  
  Comment To facilitate understanding of the connectivity patterns shown below, O atoms that connect to a single row of d4r units have been highlighted in the layer of isolated zig-zag chains shown to the right.
 
 
Connecting unit
  Connecting unit d4r    
 
References
 
    Cichocka, M.O., Lorgouilloux, Y., Smeets, S., Su, J., Wan, W., Caullet, P., Bats, N., McCusker, L.B., Paillaud, J.L. and Zou, X.D.
   "Multidimensional disorder in zeolite IM-18 revealed by combining transmission electron microscopy and X-ray powder diffraction analyses"
  Crystal Growth Des., 18, 2441-2451 (2018)

Connectivity pattern
Examples

Positions of d4r unit connectors in a row
There are two possible positions for a row of d4r units above two neighboring zig-zag chains in the layer. The position of the first d4r unit (along a) determines the positions of all the other d4r units in that row.

 
Symmetry
Operations
Translation Comment Image
0
  d4r units in position 1
1/2a
  d4r units in position 2

Disorder along b: arrangements of the rows of d4r unit connectors
The arrangement of the rows of d4r units is not necessarily periodic along b. Each row can be the same as the neighboring one or shifted by 1/2a.

Second row identical to first with no shift along aSecond row shifted by 1/2a with respect to first
 
Examples

Disorder along c: stacking of the layers
Each layer of zig-zag chains is generated from the previous one (gray) by a mirror plane (green) or an inversion center (red). The zig-zag layers themselves are ordered along c. However, the d4r units in the connecting layers can also be disordered along c, making the disorder 2-dimensional (along both b and c). The rows of d4r unit connectors can be stacked along the [001] direction using either of the following connectivity patterns

 
Symmetry
Operations
Translation* Comment Image
1/3a
  
-1/3a
  

* with respect to the previous layer


Effect on channel system
The disorder can block one or both of the straight 10-ring channels (e.g. those present in polymorphs A and B) when both d4r positions are present in a single layer of d4r units (see polymorph C).

Simplest ordered end-members


 
  Polymorph A
 
Cell Parameters: monoclinic P 1 2/m 1 (# 10)
    a = 9.0869 Å b = 7.5548 Å c = 10.4761 Å  
  α = 90.0000° β = 108.3300° γ = 90.0000°  
Ring sizes (# T-atoms): 10 8 6 5 4  
Channel dimensionality: Topological (pore opening > 6-ring): 3-dimensional  
 
In this space group and setting, the ordered connecting rows are along [001] and the layers are stacked along [100]


Note: This polymorph has NOT been observed as a pure ordered material
 
 
  Polymorph B
 
Cell Parameters: orthorhombic P m m a (# 51)
    a = 17.1828 Å b = 7.5138 Å c = 10.4477 Å  
  α = 90.0000° β = 90.0000° γ = 90.0000°  
Ring sizes (# T-atoms): 10 8 6 5 4  
Channel dimensionality: Topological (pore opening > 6-ring): 3-dimensional  
 
In this space group and setting, the ordered connecting rows are along [001] and the layers are stacked along [100]


Note: This polymorph has NOT been observed as a pure ordered material
 
 
  Polymorph C
 
Cell Parameters: monoclinic C 1 2/m 1 (# 12)
    a = 10.4455 Å b = 15.0163 Å c = 8.9577 Å  
  α = 90.0000° β = 105.5990° γ = 90.0000°  
Ring sizes (# T-atoms): 10 8 6 5 4  
Channel dimensionality: Topological (pore opening > 6-ring): 3-dimensional  
 
In this space group and setting, the ordered connecting rows are along a and the layers are stacked along [001]


Note: This polymorph has NOT been observed as a pure ordered material