Interlayer Quasi-Bonding Interactions in 2D Layered Materials: A Classification According to the Occupancy of Involved Energy Bands

Recent studies have revealed that the interlayer interaction in two-dimensional (2D) layered materials is not simply of van der Waals character but could coexist with quasi-bonding character. Herein, we classify the interlayer quasi-bonding interactions into two main categories (I: homo-occupancy interaction; II: hetero-occupancy interaction) according to the occupancy of the involved energy bands near the Fermi level. We then investigate the quasi-bonding-interaction-induced band structure evolution of several representative 2D materials based on density functional theory calculations. Further calculations confirm that this classification is applicable to generic 2D layered materials and provide a unified understanding of the total strength of interlayer interaction, which is a synergetic effect of the van der Waals attraction and the quasi-bonding interaction. The latter is stabilizing in main category H and destabilizing in main category I. Thus, the total interlayer interaction strength is relatively stronger in category II and weaker in category I.

Automated summary

Recent studies have discovered that interlayer interactions in two-dimensional layered materials can consist of both van der Waals forces and quasi-bonding character. The interactions are classified into two categories (I: homo-occupancy interaction; II: hetero-occupancy interaction) based on the occupancy of energy bands near the Fermi level. The classification provides a unified understanding of the total strength of interlayer interactions, which is a combination of van der Waals attraction and quasi-bonding interaction, showing different stabilizing effects in different categories.