Novel Functional Organic Materials and the Organic Materials Database
Electrical, magnetic and optical properties of crystals are primarily defined by their electronic structure. Electronic structure calculations based on ab initio methods are well established and widely applied. However, the exponential growth of computational power we witness nowadays and the high demand for materials prediction based on specific target properties have led to a new approach in computational materials science, referred to as materials informatics. This approach places the main effort on performing high-throughput computing as well as the development of databases and suffcient data-mining tools. One can call this approach an aggregate statistical analysis, where the properties of a single compound are captured approximately and main resource is placed on understanding global trends within the large data sets. Applications of this data-driven approach are wide-ranging and cover, for instance, the search for various functional materials with special electrical, optical and magnetic properties, including the 2016 Nobel Prize-winning topological states of matter|a prospective building block of a quantum computer. Whereas inorganic materials are well-studied by the ab initio methods, organic crystals are investigated rarely. One of the main diculties lies in the large-unit cells which can contain up to several hundred atoms. However, recent computational resources and modern code architectures have opened the path for such system sizes within the last decade. The main constituents of organic crystals are carbon, hydrogen, nitrogen, oxygen and, in rare cases, a low percentage of transition metal elements, which makes production of organics inexpensive and accessible in terms of raw materials. Organic crystals are particularly appealing for technological applications due to their softness and elastic properties. To address the need of electronic structure information for organic materials, we have developed the Organic Materials Database (OMDB) , which is freely accessible at http://omdb.diracmaterials. org. The database contains the output of thousands of calculations based on density functional theory. Instead of focusing on particular compounds, the goal of the OMDB is to develop property-related search tools for functional materials prediction. The OMDB web interface allows users to retrieve materials with specified target properties using non-trivial queries about their electronic structure, e.g., a band gap of a specific size, electronic bands following a particular pattern (linear crossing, parabolic touching, freely drawn patterns involving several bands) or similarity of band structures to a material of interest. This proposal focuses on the growth of the OMDB in terms of both number of entries and number of calculated properties to discover novel organic functional materials and its application to Dirac materials, topological semimetals, magnetic materials and efficient solar cell materials.