In order to understand how K-phonons may be responsible for the late appearance of G-phonons, we simulate the optical phonon temperature based on the above scenario where anharmonic hot phonons are involved. Our model assumes that carriers thermalize rapidly into a Fermi-Dirac distribution with a well-defined temperature and that G phonons and K phonons thermalize among themselves. The electronic system, G-phonons, and K-phonons are characterized by their temperatures Tel, TG, and TK and are linked by e-ph coupling, Γe−ph(Tel, TG/K), and ph-ph coupling between G and K-phonons, Γph−ph(TG, TK). This leads to three coupled differential equations: