Experimental and Computational Study of Electrides with Unique Dimensionality and Metastability: a 3D Electride and an Emerging Class of Dynamically Stable Electrides

This work details novel electrides, new chemistries toward their synthesis, their unique applications in ion storage, and computational simulation of these materials. Electrides with unique dimensionality and topology, particularly three-dimensional (3D) and two-dimensional (2D) electride gases, are explored. I achieve a high-purity synthesis of Ti2C and demonstrate it to be one of the first 3D electrides. A comprehensive analysis of density functional theory (DFT) calculations, experimental diffraction, spectroscopic data, and prior claims is used to convincingly solve the decades-long debate over the crystal structure of Ti2C. These results indicate that the carbon positions in this material pattern in a 3D structure, with the carbon vacancies adopting an identical pattern, which is best described as diamond cubic. DFT calculations demonstrate that electride electrons occupy the carbon vacancies of this material, revealing it to be among the first 3D electrides. I show that Ti2C is a bicontinuous material consisting of a continuous diamond-cubic crystal structure inter-penetrating a continuous symmetrical 3D electride structure. I exploit the electride sites in a hydrogenation of Ti2C, demonstrating potential application of this material in ion storage. This ion-insertion reaction proceeds via the direct substitution of hydride for electride electrons- an electron-anion exchange (EAX) reaction. I explore the use of the EAX reaction as a synthetic means toward novel electrides. I identify how EAX can be used to produce electrides in a kinetically controlled reaction to achieve electrides not limited to thermodynamic products. I use DFT to support my hypothesis that EAX can enable access to metastable electrides, a synthetic target not previously explored. In this study I identify possibly the first-known dynamically-stable electride structures including a new class of metastable 2D electrides related to the well-studied LaOAgS structure type.