Along similar lines, we maintain an open database of crystal structures ourselves at the Materials Project (materialsproject.org) at Lawrence Berkeley National Lab, which includes high-quality calculations of the electronic structure of each crystal structure so that you can do queries for the specific properties you need for your application. We're currently working alongside the Crystallography Open Database and several other databases to develop an API spec so that all similar databases can be queried in a common way: https://github.com/Materials-Consortia/optimade
If it's ok to offer an ad here, we're actually looking for someone to join our team. The calculations we offer at the Materials Project are the results of millions of CPU hours of computation, so it becomes very important that we're able to synthesize this data in a way that's approachable and understandable and then share this data effectively with other researchers, students and members of the public who might want to use it. We need help with this and we're hiring a web developer at the moment: https://news.ycombinator.com/item?id=23381358