Band (能带)theory: 能带 Energy levels split 能级 △E up when atoms interact with each other. The higher the energy level is,the wider is the energy band. The smaller the distance between atoms is,the wider the energy bandBand （能带）theory: Energy levels split up when atoms interact with each other. The higher the energy level is, the wider is the energy band. The smaller the distance between atoms is, the wider the energy band