This chapter reviews recent advances in high-pressure mineral physics of the Earth's central regions. The existence of a dense melt at the core-mantle boundary (CMB) is proposed for the ultra-low velocity zone. Possible candidates for the light elements in the core are summarized. The phase relations, compression, and sound velocity of iron-light-element alloys have been studied intensively, based on the static experiments, shock compression, and theoretical works. The chapter summarizes the present status of these works and their implications for the compositions of the outer and inner cores. To achieve a definite conclusion on the light element contents of the core, we need to establish pressure scales at the high pressure and temperature of the Earth's core, and to measure the density and sound velocity of the iron-light-element alloys covering the pressure and temperature conditions of the inner core.
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