1208.0978 (Wei-shan Lee)

Quest for Dr. Yia-Chung Chang's Calculations about the superlattice
phonon band structures    [PDF]

Wei-shan Lee

Chang and his colleagues calculated the GaAs-AlAs superlattice phonon band structures based on the Rigid-ion Model. But evidence shows that they made a mistake on the similarity transformation while assigning the three-dimensional force-constant matrices for the second-nearest neighbouring atoms. The elements in the dynamic matrix are found to be inconsistent with those published by Kunc. For materials in the diamond structure, such as Silicon, the mistake may draw to a misleading conclusion that "for Group IV, we must have E_1 = E_2 =0 to preserve symmetry." Furthermore, it is very obvious that they either assigned the non-zero parameters, E_1 and E_2 in Kunc's symbol, to be zero or they manually removed the branches having the undesired bumps, owing to the wrong symmetry property in the three-dimensional matrices, near the zone center in their phonon band structure diagram.

View original: http://arxiv.org/abs/1208.0978