Generalized evolutionary metadynamics for sampling the energy landscapes and its applications

Abstract

We present an automated scheme to systematically sample energy landscapes of crystalline solids, based on the ideas of metadynamics and evolutionary algorithms. Phase transitions are driven by the evolution of the order parameter (in this case, 6-dimensional cell vectors) and aided by atomic displacements corresponding to both zero and non-zero wave vectors, enabling cell size to spontaneously change during simulation. Our technique can be used for efficient prediction of stable crystal structures, and is particularly powerful for mining numerous low-energy configurations and phase transition pathways. By applying this method to boron, we find numerous energetically competitive configurations, based on various packings of B12 icosahedra. We also observed a low-energy metastable structure of Si(T32) which is likely to be a product of decompression on Si-II. T32 is calculated to have a quasidirect band gap of 1.28 eV, making it promising for photovoltaic applications.

Revealing and exploiting hierarchical material structure through complex atomic networks

“…The 3meV/atom energy difference between the hexagonal and cubic polytypes is small compared to the 25meV difference between cubic and hexagonal (carbon) diamond computed at the same level. The situation is very similar to that for α−B 12 , for which an alternatively packed structure of 24 atom and space group Cmcm has been identified [15], and further discussed [60,61].…”

Slicing Diamond for More sp3 Group 14 Allotropes Ranging from Direct Bandgaps to Poor Metals

“…The analogue transformation of atoms appears in the experimentally established phase transition of the two modifications of Na 2 ZnSn 5 . Such smooth rearrangements may lead to several promising element modifications, as was also computationally shown for boron networks based on shifts in the B 12 units that serve as building blocks …”

Prediction of a new ground state of superhard compound B6O at ambient conditions

“…2a,b). α-B and Cmcm -B are energetically nearly degenerate structures of boron at low pressure17, while Cmcm -B is a newly predicted structure1819. As shown in Fig.…”