High-pressure structural behavior of α-K2Ca3(CO3)4 up to 20 GPa
摘要
K-Ca double carbonates recently identified in inclusions in diamonds, as well as associated alkali-carbonate melts can play an important role in the deep carbon cycle. We studied pressure-induced changes in the crystal structure of high-pressure α-K2Ca3(CO3)4 phase up to 20 GPa using synchrotron single-crystal x-ray diffraction in diamond anvil cell. At ~ 7 GPa at room temperature the orthorhombic P212121 phase of α-K2Ca3(CO3)4 undergoes displacive phase transition into monoclinic P1121 phase. Despite the phase transition, PV-curve does not demonstrate any irregularities so that both phases can be described by the same 4th order Birch-Murnaghan equation of state with V0 = 1072.5(3) Å3, K0 = 51.1(8) GPa, K’0=3.7(3), K’’0=0.12(6).