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This study provides detailed description of a newly-discovered Callicarpa yongshunensis Wen B. Xu, Xiao D. Li & Yan Ling Liu (Lamiaceae) species from Hunan, China. The species shares similarities in the inflorescence, glandular colour and leaf shape features with C. luteopunctata H. T. Chang and C. giraldii Hesse ex Rehd., while its white fruits are similar to those of C. longifolia Lamk. However, its procumbent, evergreen shrub and white fruits are distinctly different from those of C. luteopunctata and C. giraldii, while its procumbent, scarless nodes and stellate pubescence free fruits distinguishes it from C. longifolia. Images, distribution, morphological features, molecular phylogenetic classification and conservation assessment of this new Callicarpa species are explored.

The electronic-structure evolutions of few-layer black phosphorus (BP) under pressure shows a wealth of phenomena, such as the nonmonotonic change of direct gap at the Γ point, the layer-number dependence, and the distinct responses to normal and hydrostatic pressures. A full and unified understanding to these rich phenomena remains lacking. Here, we provide a unified understanding from the competition between interlayer quasibonding (QB) interactions and intralayer chemical bonding interactions. The former decreases while the latter increases the band gap under pressure and the origin can be correlated to different combinations of inter- and intralayer antibonding or bonding interactions at the band edges. More interestingly, the interlayer QB interactions are a coexistence of two categories of interactions, namely, the coexistence of interactions between bands of the same occupancy (occupied-occupied and empty-empty interactions) and of different occupancies (occupied-empty interaction); and, the overall effect is a four-level interaction, which explains the anomalous interlayer-antibonding feature of the conduction band edge of bilayer BP. Our current study lays the foundation for the electronic-structure tuning of two-dimensional (2D) BP, and, our analysis method for multi-energy-level interactions can be applied to other 2D semiconductor homo- and heterostructures that have occupied-empty interlayer interactions.