Novel 2D allotropic forms and nanoflakes of silicon, phosphorus, and germanium: a computational study

The structural variability offered by 2D materials is an essential feature in materials design. Despite its significance, obtaining assemblies with suitable stability remains a challenge. In this work, we theoretically explore novel silicon, phosphorus, and germanium, analogues of haeckelites at hybrid DFT level. Both 2D systems and nanoflakes (NF) have been studied. All materials have been found dynamically stable; Si-, P-, and Ge- analogues of haeckelites were found to be more stable in comparison to the corresponding honeycomb structure than haeckelites in comparison with graphene. All 2D materials showed metallic behavior; however, the difference between inorganic haeckelites and the corresponding honeycomb allotropes is less than that between haeckelites and graphene. Si-, P-, and Ge-, allotropes have much higher electron affinities (EAs) compared to carbon allotropes, while haeckelites have higher EAs than honeycomb structures. Furthermore, Si-, P-, and Ge-structures also exhibit low hopping activation energies for lithium atoms. It makes these materials potentially promising as a component in Li-ion batteries.