Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li _x TiS₂ and Lithium Ion Migration in 1T-Li_0.94TiS₂

Abstract

Abstract:In many applications it has been found that the standard generalized gradient approximation (GGA) does not accurately describe weak chemical bond and electronic properties of solids containing transition metals. In this work, we have considered the intercalation material 1T-Li x TiS 2 (0 ≤ x ≤ 1) as a model system for the evaluation of the accuracy of GGA and corrected GGA with reference to the availabile experimental data. The influence of two different dispersion corrections (D3 and D-TS) and an on-site Coulomb repulsion term (GGA + U) on the calculated structural and electronic properties is tested. All calculations are based on the Perdew-Burke-Ernzerhof (PBE) functional. An effective U value of 3.5 eV is used for titanium. The deviation of the calculated lattice parameter c for TiS 2 from experiment is reduced from 14 % with standard PBE to −2 % with PBE + U and Grimme's D3 dispersion correction. 1T-TiS 2 has a metallic ground state at PBE level whereas PBE + U predicts an indirect gap of 0.19 eV in agreement with experiment. The 7 Li chemical shift and quadrupole coupling constants are in reasonable agreement with the experimental data only for PBE + U-D3. An activation energy of 0.4 eV is calculated with PBE + U-D3 for lithium migration via a tetrahedral interstitial site. This result is closer to experimental values than the migration barriers previously obtained at LDA level. The proposed method PBE + U-D3 gives a reasonable description of structural and electronic properties of 1T-Li x TiS 2 in the whole range 0 ≤ x ≤ 1.

Optoelectronic Properties of TiS2: A Never Ended Story Tackled by Density Functional Theory and Many-Body Methods

“…Conflicts concern its real electrical behavior. − In other terms, does stoichiometric TiS 2 have to be described as a semimetal or a low-gap semiconductor? Many theoretical investigations argue that the compound should be a semiconductor − other calculations lead to a semimetallic behavior. ,,,, From the experimental point of view, this question still remains open because of the reported propensity of the material to be naturally slightly off-stoichiometric with the insertion of Ti atoms in the van der Waals gap, i.e., between two 2 / ∞ [TiS 2 ] slabs built upon [TiS 6 ] octahedra sharing edges. This singularly complicates the assignment of the TiS 2 electrical behavior because the experimentalist cannot certify the exact chemical composition of the material on which the physical properties are collected.…”

Multiscale Investigation into the Co‐Doping Strategy on the Electrochemical Properties of Li2RuO3 Cathodes for Li‐Ion Batteries

“…The U values used for transition metals in the studied cathodes are extracted from the literature [37,38] and are summarized in Table 1. Same as other researches, [39][40][41][42][43] the U values have been selected to optimize the calculated energy. Figure 2 shows that these U values produce results that are in good agreement with the experimental data.…”

Anion substitution and influence of sulfur on the crystal structures, phase transitions, and electronic properties of mixed TiO2/TiS2 compounds

“…1(c)] (Rimmington & Balchin, 1974;McKelvy & Glaunsinger, 1987;Patel & Balchin, 1984). Considering the electronic structure of TiS 2 , many conflicting results exist, ranging from semi-metallic (Fang et al, 1997;Ivanovskaya & Seifert, 2004;Li et al, 2005;Yu et al, 2010;Xu et al, 2015;Liu et al, 2011;Samanta et al, 2014) to semiconductor behavior (Ryzhikov et al, 2014;Li et al, 2006;Beaumale et al, 2014;Gatensby et al, 2014;Zhu et al, 2013;Zhang et al, 2006;Gü ller et al, 2012;Bandura & Evarestov, 2014;Werth et al, 2017). Experiments also leave this question open because there are reports about naturally slightly offstoichiometric TiS 2 , with the insertion of Ti atoms in the van der Waals gap.…”