The dynamics and electronic structure of the magic ${\mathrm{Na}}_{40}$ cluster are studied as a function of temperature using an ab initio molecular dynamics method. ${\mathrm{Na}}_{40}$ is found to undergo a structural transition which can be identified as melting by traditional indicators. Melting transition was observed in the region 300–350 K with a latent heat of melting of 11 meV/atom, which is 42% of the bulk value. Octupole deformation is the dominating type of multipole deformations in the temperature range studied (150–550 K). The stability of the deformation type is indicated by the persistently large HOMO-LUMO gap, both in the solid and liquid phases.

• Received 20 January 1998

DOI:https://doi.org/10.1103/PhysRevLett.80.3940