Long-time (~1 ns region) molecular dynamics (MD)simulations of lithium metasilicate (Li2SiO3) and amixed-alkali silicate (LiKSiO3) glass have been performed toconfirm the mechanism of the `mixed-alkali effect'. The motion oflithium ions in lithium metasilicate (Li2SiO3) glass isdivided into slow (A) and fast (B) categories in the glassy state.The waiting time distribution of the jump motion of each componentshows a power-law behaviour with different exponents. The slowdynamics is caused by localized jump motions and by the long waitingtime. On the other hand, the fast dynamics of the lithium ions inLi2SiO3 is characterized as Lévy flight caused bycooperative jumps. Short intervals between jump events also occur infast dynamics, in the short-time region. The main diffusion andconduction processes of silicate glasses are not the single jumpsbut the cooperative jumps. A component with accelerated dynamics isalmost absent in the mixed-alkali system. The contributions of thetemporal and spatial aspects of the particle dynamics are separated.A large change in the spatial parameters has been observed onmixing, and interception of the jump path by other kinds of ion pathsuppresses the cooperative jump process. On the other hand, inlonger-time regions, motion of the framework has been found toaccompany the small number of events where alkali metal ions jump tounlike-ion sites. Thus both loosening of the glass structure and areduction of ionic diffusion coefficients occur in the mixed-alkalisystem.