We conduct molecular dynamics simulations of the ejection process from a grooved Pb surface subjected to supported and unsupported shock waves with various shock-breakout pressures（PSB） inducing a solid–liquid phase transition upon shock or release. It is found that the total ejecta mass changing with PSBunder a supported shock reveals a similar trend with that under an unsupported shock and the former is always less than the latter at the same PSB. The origin of such a discrepancy could be unraveled that for an unsupported shock, a larger velocity difference between the jet tip and its bottom at an early stage of jet formation results in more serious damage, and therefore a greater amount of ejected particles are produced. The cumulative areal density distributions also display the discrepancy. In addition, we discuss the difference of these simulated results compared to the experimental findings.
