I agree with the other answer but there are many other resources:
- Open Crystallographic Database which includes a large set of experimental crystal structures.
- There's a related Theoretical Crystallographic Open Database
- For zeolites, there's the IZA Database
- For MOFs, there's the CoRE MOF database
- Aflow also has a good repository
- NOMAD has a variety of materials data, including geometries
There is the Materials Project:
From the site: Harnessing the power of supercomputing and state of the art electronic structure methods, the Materials Project provides open web-based access to computed information on known and predicted materials as well as powerful analysis tools to inspire and design novel materials.
From the experimental view, there are databases like ICDD (http://www.icdd.com/) with the x-ray crystallographic determined structures.
Depending on what kind of materials looking for the following crystallographic databases can be relevant, too (unfortunately, for a cost):
In addition to above recommendations, I also use American Mineralogist Crystal Structure Database.
The good thing about this place is that you can check the publications related to a specific geometry.
I usually use AMCSD and Materialsproject.
An open computational database of two-dimensional materials. A large dataset of 2D materials, with more than 6,000 monolayer structures, obtained from both top-down and bottom-up discovery procedures
Results from screening all known 3D crystal structures finding those that can be computationally exfoliated producing 2D materials candidates.
The database contains the results of high-throughput first-principles screening of known crystal structures for topological materials (topological insulators, Dirac and Weyl semimetals, etc.).
I recently came across the publication Data‐Driven Materials Science: Status, Challenges and Perspectives by Himanen et. al featuring this list of current major materials data infrastructures.
- Himanen, Lauri, et al. "Data‐Driven Materials Science: Status, Challenges, and Perspectives." Advanced Science 6.21 (2019): 1900808.