Targeting high symmetry in structure predictions by biasing the potential energy surface

• Published in: Physical review research Vol. 5; no. 1; p. 013189
• Main Authors: Huber, Hannes, Sommer-Jörgensen, Martin, Gubler, Moritz, Goedecker, Stefan
• Format: Journal Article
• Language: English
• Published: American Physical Society 01.03.2023
• ISSN: 2643-1564; 2643-1564
• DOI: 10.1103/PhysRevResearch.5.013189

Ground-state structures found in nature are, in many cases, of high symmetry. But structure prediction methods typically render only a small fraction of high-symmetry structures. Especially for large crystalline unit cells, there are many low-energy defect structures. For this reason, methods have been developed where either preferentially high-symmetry structures are used as input or where the whole structural search is done within a certain symmetry group. In both cases, it is necessary to specify the correct symmetry group beforehand. However, it can in general not be predicted which symmetry group is the correct one leading to the ground state. For this reason, we introduce a potential energy biasing scheme that favors symmetry and where it is not necessary to specify any symmetry group beforehand. On this biased potential energy surface, high-symmetry structures will be found much faster than on an unbiased surface and independently of the symmetry group to which they belong. For our two test cases, i.e., a C_{60} fullerene and bulk silicon carbide, we get speedups of 25 and 63. In our data, we also find a clear correlation between the similarity of the atomic environments and the energy. In low-energy structures, all the atoms of a species tend to have similar environments.