See what you will probably never see in reality, thanks to the PCOD

Two-dimensional SiO2 models (not DFT-optimized) as predicted by GRINSP

They can be porous too...

Models selected among 11157 CIF including 3D, 2D and 1D SiO2

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.
2- Predicted corner-sharing titanium silicates. A. Le Bail, Z. Kristallogr., Suppl. 26 (2007) 203-208.
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 or zipped)
4- Advances in structure prediction of inorganic compounds. A. Le Bail, Report of 2nd Algerian Crystallography Congress, Algérie (2005).
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: 10.1039/c003907c
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

PCOD1000004   CIF

PCOD900003   CIF   same as before but less distorted, smaller cell

PCOD3000624   CIF

PCOD3005178   CIF

PCOD3005151   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

PCOD3004329   CIF

PCOD3007243   CIF

PCOD3004896   CIF

PCOD3003565   CIF

PCOD3007213   CIF

PCOD3009950   CIF

PCOD670009   CIF

PCOD3000213   CIF

PCOD3003939   CIF

PCOD3003044   CIF

PCOD3003929   CIF

PCOD3003930    CIF

PCOD3001602   CIF

PCOD3004060   CIF

PCOD3003566   CIF

PCOD3001752   CIF

PCOD3004760   CIF

PCOD3004939   CIF

PCOD3001747   CIF

PCOD3003932   CIF

PCOD3001268   CIF

PCOD3101399  CIF

PCOD3103687   CIF

PCOD3103321   CIF

PCOD3102839   CIF

PCOD3102426   CIF

PCOD3102120   CIF

PCOD3000230   CIF

PCOD3103838   CIF

PCOD3102266   CIF

PCOD3103126   CIF

PCOD3100471   CIF

PCOD3102255   CIF

PCOD3100607   CIF

PCOD3100282   CIF

PCOD3102142   CIF

3109046   CIF

PCOD3109269   CIF

PCOD3103474   CIF

PCOD3109101   CIF

PCOD3108373   CIF

PCOD3103427   CIF

PCOD3004909   CIF

PCOD3004748   CIF

PCOD3003951   CIF

PCOD3002753   CIF

PCOD3000993   CIF