Periodic Building Unit (PerBU):  Layer of isolated zigzag 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 zigzag chains shown to the right. 

Connecting unit  d4r  
Examples 

Second row identical to first with no shift along a  Second row shifted by 1/2a with respect to first 
Examples 
 
^{*} relative to the previous layer of connectors 
Polymorph EOS  
Cell Parameters:  monoclinic  P 1 2/m 1 (# 10)  
a = 9.0869 Å  b = 7.5548 Å  c = 10.4762 Å  
α = 90.000°  β = 108.333°  γ = 90.000°  
Volume =  682.7 Å^{3}  
Framework Density (FD_{Si}):  17.6 
Ring sizes (# Tatoms):  10 8 6 5 4  
Channel dimensionality:  Topological (pore opening > 6ring): 3dimensional 
Composite Building Units: 
d4r  mtw  
Note: This polymorph corresponds to the ordered framework EOS  
Polymorph IM18_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°  
Volume =  1348.9 Å^{3}  
Framework Density (FD_{Si}):  17.8 
Ring sizes (# Tatoms):  10 8 6 5 4  
Channel dimensionality:  Topological (pore opening > 6ring): 3dimensional 
Maximum diameter of a sphere:  
that can be included  5.1 Å  
that can diffuse along  a: 3.88 Å  b: 4.54 Å  c: 2.88 Å  
[0 1 0] : 4.54 Å  
addional volume data 
Composite Building Units: 
d4r  mtw  
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 ITW  
Cell Parameters:  monoclinic  C 1 2/m 1 (# 12)  
a = 10.4496 Å  b = 15.0277 Å  c = 8.9537 Å  
α = 90.000°  β = 105.640°  γ = 90.000°  
Volume =  1354.0 Å^{3}  
Framework Density (FD_{Si}):  17.7 
Ring sizes (# Tatoms):  8 6 5 4  
Channel dimensionality:  Topological (pore opening > 6ring): 2dimensional 
Maximum diameter of a sphere:  
that can be included  4.73 Å  
that can diffuse along  a: 2.78 Å  b: 1.54 Å  c: 3.95 Å  
addional volume data 
Composite Building Units: 
d4r  
In this space group and setting, the ordered connecting rows are along [001] and the layers are stacked along [100] 
Note: This polymorph corresponds to the ordered framework ITW  