Ab initio simulation of laser-induced transformations in fullerite

We studied by ab initio molecular dynamics the modifications induced on fullerite by irradiation with ultrashort, very intense laser pulses. We identified the threshold for the nonthermal cage opening of the ${\mathrm{C}}_{60}$ molecules that is the analog of the laser-induced nonthermal melting observed in semiconductors and graphite. The new phase formed by the nonthermal coalescence of the ${\mathrm{C}}_{60}$ molecules is fluidlike and mainly formed by small chains of twofold-coordinated atoms. An estimate of the threshold laser fluence for the nonthermal transformation is given.