Electronic-excitation-induced solid-to-solid amorphization in GST. (a)–(f) Structural snapshots during the AIMD simulation of amorphization under a 9% excitation. The crystalline structure turns to a disordered phase within 24 picoseconds (ps). (g) Mean square distances (MSD) during the AIMD simulations of the excitation-induced amorphization and the normal melting. The blue line indicates the exited state (Exc.) while the red line represents the melting state (Mel.). (h) The change of amorphization temperatures with different excitation intensities. The data are obtained from a series of AIMD simulations with different excitation intensities and temperatures. The red line is a quadratic fitting. (i) Partial density of states of GST. Upon a laser excitation, electrons are mainly excited from valence band maximum, i.e., the region labelled by “j”. Panels (j) and (k) show the projected electronic density distribution of the energy regions indicated by “j” and “k” in panel (i), respectively. Obviously, for the band-edge excitation, Ge atoms contribute more electronic states than Sb atoms. Panels (a)–(g) and (i)–(k) are reproduced from Ref. [26] with permission from the American Physical Society. Panel (h) is reproduced from Ref. [25] with permission from the John Wiley and Sons.