Electronic structure of TiSe\(_2\) from a quasi-self-consistent G\(_0\)W\(_0\) approach

• Published in: arXiv.org
• Main Authors: Hellgren, Maria, Lucas Baguet, Calandra, Matteo, Mauri, Francesco, Wirtz, Ludger
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 02.02.2021
• Subjects: Approximation; Charge density waves; Density functional theory; Electronic structure; Exchanging; First principles; High temperature; Low temperature; Mathematical analysis; Parameters
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2005.14603

In a previous work it was shown that the inclusion of exact exchange is essential for a first principles description of both the electronic- and the vibrational properties of TiSe\(_2\), M. Hellgren et al. [Phys. Rev. Lett. 119, 176401 (2017)]. The \(GW\) approximation provides a parameter-free description of screened exchange but is usually employed perturbatively (\(G_0W_0\)) making results more or less dependent on the starting point. In this work, we develop a quasi-self-consistent extension of \(G_0W_0\) based on the random phase approximation (RPA) and the optimized effective potential of hybrid density functional theory. This approach generates an optimal \(G_0W_0\) starting-point and a hybrid exchange parameter consistent with the RPA. While self-consistency plays a minor role for systems such as Ar, BN and ScN, it is shown to be crucial for TiS\(_2\) and TiSe\(_2\). We find the high-temperature phase of TiSe\(_2\) to be a semi-metal with a band structure in good agreement with experiment. Furthermore, the optimized hybrid functional agrees well with our previous estimate and therefore accurately reproduces the low-temperature charge density wave phase.