AbstractWhen a solid is subject to an intense electronic excitation, it is expected that its cohesive properties differ from the non‐excited state. The variation of crystal instability temperature,Tc, with the concentration of excited electron–hole pairs is examined theoretically. Using a phenomenological model of electron–phonon–defect interactions, it is shown thatTcdecreases quasi‐linearly with increasing electron–hole pair density. The consequences of this on diffraction broadening, threshold energy for transformation, premelting, and optical properties ar