**1. Introduction and Scope**

Materials used under extreme conditions are important in various industrial and defense fields [1,2]. The performance of these materials critically affects the lifetime of related facilities [1,2]. Thus, it is essential to explore the underlying damage mechanisms of materials under extreme conditions. Considering the difficulty and high cost of the experiments carried out to investigate these mechanisms, numerical modeling of the material response is crucial for study in these fields [3,4]. Until now, although various approaches and models from the atomic scale to the macroscale have been used or developed to simulate the mechanical response and microstructural evolution during the processes [4–8], detailed investigations are still needed to further understand the materials under extreme conditions.

The scope of this Special Issue embraces numerical work on material responses to extreme conditions such as high-speed impact or loading, neutron or ion irradiation, and high-pressure and/or high-temperature environment. Related simulation results based on the first-principle molecular dynamics and finite element methods are reported.
