We prove that the answer of stationary wave under cyclic boundary condition that has double length of the monatomic chain is the same as the answer under reflecting boundary condition.

• 本文还证明了镜面反射边界条件的解与2 倍原子链长度循环边界条件下的驻波解是等价的,说明采用循环边界条件近似求解有它的合理性;