In perovskite-type strontium titanate (SrTiO 3 ) 〈110〉 dislocations, which are the main carriers of plastic flow at low temperature, lose their mobility as temperature increases, leading to brittle failure above 1050 K. We present theoretical evidence for a change in their core structure into a sessile, climb-dissociated configuration at high temperature. This mechanism is shown to operate in both SrTiO 3 and MgSiO 3 , indicating that it may be a general feature of perovskite-type materials. It follows that the activity of the 〈110〉 slip system depends critically on the strain rate-temperature couple, ð _ ε; TÞ.The discovery of the atypical mechanical behavior of strontium titanate (SrTiO 3 or STO) and its double ductile-brittle-ductile transition [1,2] has challenged our understanding of the plastic behavior of perovskite-type materials, and has since motivated several studies. A series of experiments [3,4] and simulations [5,6] have provided a good understanding of the ductile behavior of STO at low temperature and demonstrated its direct link with the glide of 〈110〉 dislocations. However it is still unclear why this mechanism becomes inactive at high temperature, leading to brittle failure above 1050 K. It was initially proposed that 〈110〉 dislocations become sessile by dissociating into two 〈100〉 dislocations, or because of a change of preferential slip plane [2]. Later it was proposed that 〈110〉 dislocations dissociate by climb at high temperature, into a configuration similar to the one observed in low-angle tilt grain boundaries [7,3]. Despite arguments in favor of the latter [8], there has been no direct evidence for this change of core structure, the mechanisms by which it operates are still unknown, and whether this transition is specific to STO or a general feature of perovskite-type materials remains an open question.In this work we investigate the effect of temperature on the core structure of individual [110] pc edge dislocations in two perovskitetype materials: the cubic strontium titanate, and the orthorhombic, high-pressure magnesium silicate MgSiO 3 which is the pure Mg endmember of bridgmanite [9], the main constituent of the Earth's lower mantle. In the following we consider MgSiO 3 under the hydrostatic pressure of 30 GPa, corresponding to a depth of ca. 700 km i.e. the uppermost lower mantle. Throughout this article crystal directions are given in the (pseudo-)cubic reference, noted with the subscript "pc", for easier comparison between the two materials (in MgSiO 3[110] pc = [100]; ½110 pc ¼ ½010 ; 2[001] pc = [001], see e.g. Ref.[10]). The 〈110〉 pc dislocations belong to the easiest slip system in both materials [11], [6]. Atomic systems were constructed with Atomsk [12], and classical molecular statics and dynamics simulations were performed with LAMMPS [13]. Interatomic interactions in SrTiO 3 were modeled with the rigid-ion potential proposed by Thomas et al. [14], and in MgSiO 3 with the one from Alfredsson et al. [15].The glide-dissociated core structures of [110] pc edge dislocation...