“…Compared with an ionic crystal, the "vibrational" conductivity component observed in a glass is, therefore, much broader, extending to lower frequencies. Figure 5 shows the example of a silver thiogermanate glass [39,40]. In this log-log representation of the total (ionic) conductivity, σ (ν), the contribution due to vibrations is seen to have a slope of two on its low-frequency flank, which is known to be the usual behaviour in ionic solids [41].…”