The Einstein solid is made up of single-frequency quantum harmonic oscillators, ϵ = �?ω = h ν displaystyle epsilon =hbar omega =hnu The Slice-off frequency can be established within the cut-off wavelength. From your sampling theorem, we are aware that for wavelengths smaller than two a displaystyle 2a The approximation https://x.com/hongyuxin20/status/1817802989299814645