“…The enthalpy data related to the phase transition clearly split into two groups characterized by unusually large values (group 1: 45-55 kJ mol −1 -K 3 CeCl 6 , K 3 PrCl 6 , K 3 NdCl 6 and Rb 3 LaCl 6 ), on the one hand, and by noticeably smaller values (group 2: only 7-9 kJ mol −1 -K 3 TbCl 6 , Rb 3 CeCl 6 , Rb 3 PrCl 6 , Rb 3 NdCl 6 , Rb 3 TbCl 6 and all the Cs 3 LnCl 6 compounds), on the other [2,8,9]. According to literature information [10][11][12][13][14][15], the large enthalpy effect in the first group corresponds to formation of M 3 LnCl 6 compounds from MCl and M 2 LnCl 5 and is described as a "reconstructive phase transition". The M 3 LnCl 6 compounds in this group have a single, high-temperature crystal modification.…”