Charge density waves (CDWs) in transition metal dichalcogenides are the subject of growing scientific interest due to their rich interplay with exotic phases of matter and their potential technological applications. Here, using density functional theory with advanced meta-generalized gradient approximations (meta-GGAs) and linear response time-dependent density functional theory (TDDFT) with state-of-the-art exchange-correlation kernels, we investigate the electronic, vibrational, and optical properties in 1T-TiSe₂ with and without CDW. In both bulk and monolayer TiSe₂, the electronic bands and phonon dispersions in either normal or CDW (semiconducting) phase are described well via meta-GGAs, which separate the valence and conduction bands just as HSE06 does but with significantly more computational feasibility. The experimentally observed humps of electron energy loss spectroscopy are successfully reproduced in TDDFT. Our work opens the door to simulating these complexities in CDW compounds from first principles by revealing meta-GGAs as an accurate low-cost alternative to HSE06.

过渡金属二硫属化物中的电荷密度波（CDW）因其与奇异物质相的丰富相互作用及其潜在的技术应用而受到越来越多的科学兴趣。在这里，我们使用具有先进元广义梯度近似（meta-GGA）的密度泛函理论和具有最先进交换相关核的线性响应时间相关密度泛函理论（TDDFT），研究了电子、振动、以及具有和不具有 CDW 的 1 T -TiSe ₂的光学特性。在体相和单层 TiSe ₂中，正常相或 CDW（半导体）相中的电子能带和声子色散都可以通过元 GGA 很好地描述，它可以像 HSE06 一样分离价带和导带，但具有更高的计算可行性。实验观察到的电子能量损失谱的驼峰在 TDDFT 中成功再现。我们的工作揭示了元 GGA 作为 HSE06 的准确低成本替代品，为从第一原理模拟 CDW 化合物中的这些复杂性打开了大门。