See what you will probably never see in reality, thanks to the PCOD
Two-dimensional SiO2 models (not DFT-optimized) as predicted
They can be porous too...
Models selected among 11157 CIF including 3D, 2D and 1D
To be compared to the 4 models in a 2017 paper
Not exhaustive list (much more will be added during the next weeks)...
References for these predictions :
1- Inorganic structure prediction with GRINSP. A. Le Bail, J. Appl. Cryst.
38 (2005) 389-395. http://journals.iucr.org/j/issues/2005/02/00/cg5019/
2- Predicted corner-sharing titanium silicates. A. Le Bail, Z. Kristallogr.,
Suppl. 26 (2007) 203-208. https://www.researchgate.net/publication/228093494_Predicted_corner-sharing_titanium_silicates
3- Powerpoint file : Contribution to the "Gordon Conference Style" Workshop
: Global Optimisation Techniques Applied to the Prediction of Structures,
5-7 July 2006, University College London (.ppt
4- Advances in structure prediction of inorganic compounds. A. Le Bail,
Report of 2nd Algerian Crystallography Congress, Algérie (2005). http://arxiv.org/abs/cond-mat/0606025
5- Hypothetical AlF3 crystal structures, A. Le Bail, F.
Calvayrac, J. Solid State Chem., 179 (2006) 3159-3166.
6- Inorganic structure prediction: too much and not enough, A. Le Bail,
Solid State Phenomena 130 (2007) 1-6.
7- Frontiers between crystal structure prediction and determination by
powder diffractometry, A. Le Bail, Powder Diffraction, S23 (2008) S5-S12.
8- Databases of virtual inorganic crystal structures and their applications,
A. Le Bail, Phys. Chem. Chem. Phys. 12 (2010) 8521-8530. DOI:
Etc - search by yourself after all...
A- Simplest models : two-sheets-related-by-a-mirror
PCOD3007286 (α-2D-silica in the paper cited above) CIF
PCOD670014 - close to the previous one but not exactly - CIF
B- More complex models, though the first three are one-sheet thick :
PCOD1150104 (δ-2D-silica in the paper cited above) CIF
PCOD1000001 (β-2D-silica in the paper cited above) CIF
PCOD740002 another organization similar to the two previous ones - CIF
PCOD1150331 (γ-2D-silica in the paper cited above) CIF