声子谱计算中动力学矩阵的约化

以（4，2）型手性碳纳米管为例，介绍利用晶体的对称性建立约化矩阵的方法．通过约化矩阵，将动力学矩阵约化成准对角形式，求解准对角形式的动力学矩阵得到本征值与本征矢．与直接求解动力学矩阵相比，经过约化处理的计算过程大幅度节省计算时间，并且计算结果按振动模对称性排序，省去分析本征矢判断本征值所属振动模对称性的步骤．

Reduction of Dynamical Matrix in Phonon Spectra Calculation

Taking （4,2） chiral carbon nanotube as an example, we discussed the establishment of a reduced matrix based on crystal symmetry. The dynamical matrix was reduced to quasi diagonal form by reduced matrix to obtain the eigenvalues and eigenvectors of the matrix. Compared with the unreduced dynamical matrix, the reduced matrix can greatly reduce the computation time and the results were sequenced according to the symmetry of vibration mode. Therefore, analysis of the sym- metry of vibration mode became unnecessary.