With nonzero on-site potential,the frequency of acoustic branch at the center of Brillioun zone is nonzero,and the frequency increases with the on-site potential increasing.

• 在位势使色散关系声频支在布里渊区中心的振动频率不再为零；并且随在位势的增大而增大.；对于原子之间相互作用势不随在位势大小变化的情况下；晶格振动的色散关系的频隙随在位势的增大而变宽