3 Tests and applications

Here we discuss tests of USPEX on system with well-known stable phases and also show how our method finds hitherto unknown structures. The test cases (including ice, methane, ammonia, carbon dioxide, benzene, glycine and butane-1,4-diammonium dibromide, etc) cover a wide range of systems with different molecular shapes (tetrahedral, linear, bent, planar and small biomolecules), and chemical interactions (vdW dispersion, ionic, covalent and metallic bonding, strong/weak hydrogen bonding, $\pi $-$\pi $ stacking, organic and inorganic molecular systems, etc). All the calculations discussed below were performed in the framework of DFT or DFT+D. Driven by the USPEX code, the structures were initially relaxed in SIESTA with constrained molecular geometry and then fully relaxed in VASP at the final stages.