Ag atoms 1 Atoms 1 Copper compounds 1 Crystal atomic structure 1 Crystal symmetry 1 Cu atoms 1 Dynamic matrix 1 Dynamics 1 Eigenvalues and eigenfunctions 1 Force constants 1 Germanium compounds 1 Lattice constants 1 Lattice vibrations 1 Modulation 1 Modulation vectors 1 Phonon spectrum 1 Phonons 1 Selenium compounds 1 Silicon compounds 1 Silver 1 Silver compounds 1 Spatial symmetry 1 Spectrum calculation 1 Super-spatial symmetry 1 dynamic matrix 1 force constant 1 matrix 1 modulation vector 1 phonon spectrum 1 super-spatial symmetry