Ultrafast Transitions in X‐Ray Irradiated Solids

ABSTRACT In this review, we present current developments on modeling ultrafast transitions in solids triggered by intense, atto‐ to femtosecond pulses from X‐ray free electron lasers. This specific irradiation regime requires dedicated simulation tools based on theoretical and computational methods, involving the elements of classical and quantum physics. Our in‐house codes, XCASCADE‐3D, XTANT, and XSPIN, can follow various X‐ray‐induced transitions in irradiated solids, ranging from purely electronic transitions, changing solid's optical and magnetic properties to rapid structural changes, bringing the irradiated material into the warm‐dense‐matter, or plasma state.