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确定所选碳酸盐固溶体在压力(P)高达80 GPa和温度(T)高达1000 K下的相行为。虽然室温测量将在Mao型活塞缸金刚石砧池（DAC）中进行，但在高P和高T联合条件下，将使用带有内部垫圈加热器（DAC- ht）的DAC进行实验。此外，我们将通过收集和解释可见光到近红外（VIS到近红外）光谱范围内的光谱来记录不同压力下几种碳酸盐中Fe2+的电子态，并研究Fe2+高自旋到低自旋状态转变的P和T条件。将在密度泛函理论（DFT）和分子动力学模拟的框架下进行互补电子结构计算，以将各自碳酸盐的电子和原子结构以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建议中所述的研究单位的目标，即了解过渡带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.