Modern advances in generating ultrabright electron beams have unlocked unprecedented experimental advances based on synchrotron radiation. Current challenges lie in improving the quality of electron sources with novel photocathode materials such as alkali-based semiconductors. To unleash their potential, a detailed characterization and prediction of their fundamental properties is essential. In this work, we employ density functional theory combined with machine learning techniques to probe the thermodynamic stability of various alkali antimonide crystals, emphasizing the role of the approximations taken for the exchange-correlation potential. Our results reveal that the SCAN functional offers an optimal trade-off between accuracy and computational costs to describe the vibrational properties of these materials. Furthermore, it is found that systems with a higher concentration of Cs atoms exhibit enhanced anharmonicities, which are accurately predicted and characterized with the employed methodology.
Ab initio study of the crystal and electronic structure of mono- and bi-alkali antimonides: Stability, Goldschmidt-like tolerance factors, and optical properties
First-principle study of paraelectric and ferroelectric CsH$_2$PO$_4$ including dispersion forces: stability and related vibrational, dielectric and elastic properties
利用密度泛函理论（DFT）和密度泛函微扰理论（DFPT）研究了铁电材料CsH $_2$ PO $_4$的低温稳定性和响应函数.这种材料不能用DFT中通常的（半）局部近似来描述。远程e $^-$ -e $^-$相关性需要适当考虑，例如，使用Grimme的DFT-D方法，如在这项工作中所研究的。我们发现DFT-D3（BJ）对二氢化碱金属磷酸盐家族（KH $_2$ PO $_4$，RbH $_2$ PO $_4$，CsH $_2$ PO $_4$）的成员表现最好，导致实验晶格参数重现平均偏差为0.5%。利用这些DFT-D方法，CsH $_2$ PO $_4$的结构、介电、振动和机械性质与现有实验（$<$ 2%MAPE用于拉曼活性声子）总体上非常一致。我们的研究表明，可能存在一个新的低温相CsH $_2$ PO $_4$，还没有实验报告。最后，我们报告的实施DFT-D的弹性常数内的DFPT的贡献。
