Structural, electronic and thermodynamic properties of carbonates at high pressures andtemperatures by in situ spectroscopy and atomic-scale simulations

该项目的科学目标是通过振动光谱法在压力（P）高达80 GPa和温度（T）高达1000 K的条件下确定选定的碳酸盐固溶体的相行为。虽然室温测量将在Mao型活塞圆柱金刚石对顶砧单元（DAC）中进行，但具有内部垫圈加热器的DAC（DAC-HT）将用于在组合的高P和高T条件下的实验。我们还将通过收集和解释可见光到近红外（维斯到NIR）光谱范围内的光谱，记录不同压力下几种碳酸盐中Fe 2+的电子态，并研究Fe 2+高自旋到低自旋态跃迁的P und T条件。将在密度泛函理论（DFT）和分子动力学模拟的框架内进行补充电子结构计算，以将相应碳酸酯的电子和原子结构及动力学与其振动和热力学性质联系起来。这项研究将有助于实现主要提案中所述的研究股的目标，即了解过渡区和下地幔条件下碳酸盐的相关系、晶体化学、物理性质和反应。

The scientific goal of this project is to determine the phase behavior of selected carbonate solid solutions by vibrational spectroscopy at pressures (P) up to 80 GPa and temperatures (T) up to 1000 K. While room temperature measurements will be performed in Mao type piston cylinder diamond anvil cells (DAC), DACs with internal gasket heaters (DAC-HT) will be employed for experiments at combined high P and high T conditions. We will additionally document the electronic state of Fe2+ in several carbonates at different pressures by collecting and interpreting optical spectra in the visible to nearinfrared (VIS to NIR) spectral range, and investigate the P und T conditions of Fe2+ highspin to lowspin state transitions. Complementary electronic structure calculations in the framework of density functional theory (DFT) and molecular dynamics simulations will be performed to link the electronic and atomic structure and dynamics of the respective carbonates to their vibrational and thermodynamic properties. This study will contribute to the goals of the Research Unit as described in the main proposal, i.e. to the understanding of phase relations, crystal chemistry, physical properties, and reactions of carbonates at conditions of the transition zone and the lower mantle.