1
|
Pal B, Cao Y, Liu X, Wen F, Kareev M, N'Diaye AT, Shafer P, Arenholz E, Chakhalian J. Anomalous orbital structure in two-dimensional titanium dichalcogenides. Sci Rep 2019; 9:1896. [PMID: 30760747 PMCID: PMC6374443 DOI: 10.1038/s41598-018-37248-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 11/05/2018] [Indexed: 11/30/2022] Open
Abstract
Generally, lattice distortions play a key role in determining the electronic ground states of materials. Although it is well known that trigonal distortions are generic to most two dimensional transition metal dichalcogenides, the impact of this structural distortion on the electronic structure and topological properties has not been understood conclusively. Here, by using a combination of polarization dependent X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and atomic multiplet cluster calculations, we have investigated the electronic structure of titanium dichalcogenides TiX2 (X = S, Se, Te), where the magnitude of the trigonal distortion increase monotonically from S to Se and Te. Our results reveal the presence of an anomalously large crystal field splitting. This unusual kind of crystal field splitting is likely responsible for the unconventional electronic structure of TiX2 compounds and ultimately controls the degree of the electronic phase protection. Our findings also indicate the drawback of the distorted crystal field picture in explaining the observed electronic ground state and emphasize the key importance of trigonal symmetry, metal-ligand hybridization and electron-electron correlations in defining the electronic structures at the Fermi energy.
Collapse
Affiliation(s)
- Banabir Pal
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA.
| | - Yanwei Cao
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA. .,Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, 315201, China.
| | - Xiaoran Liu
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| | - Fangdi Wen
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| | - M Kareev
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| | - A T N'Diaye
- Advanced Light Source, Lawrence Berkley National Laboratory, Berkeley, California, 94720, USA
| | - P Shafer
- Advanced Light Source, Lawrence Berkley National Laboratory, Berkeley, California, 94720, USA
| | - E Arenholz
- Advanced Light Source, Lawrence Berkley National Laboratory, Berkeley, California, 94720, USA
| | - J Chakhalian
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| |
Collapse
|
2
|
Werth V, Volgmann K, Islam MM, Heitjans P, Bredow T. Density Functional Theory Evaluated for Structural and Electronic Properties of 1T-Li
x
TiS2 and Lithium Ion Migration in 1T-Li0.94TiS2. Z PHYS CHEM 2017. [DOI: 10.1515/zpch-2016-0919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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
TiS2 (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 TiS2 from experiment is reduced from 14 % with standard PBE to −2 % with PBE+U and Grimme’s D3 dispersion correction. 1T-TiS2 has a metallic ground state at PBE level whereas PBE+U predicts an indirect gap of 0.19 eV in agreement with experiment. The 7Li 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
TiS2 in the whole range 0≤x≤1.
Collapse
Affiliation(s)
- Vanessa Werth
- Institut für Physikalische Chemie und Elektrochemie , Leibniz Universität Hannover , Callinstr. 3-3a , 30167 Hannover , Germany
| | - Kai Volgmann
- Institut für Physikalische Chemie und Elektrochemie , Leibniz Universität Hannover , Callinstr. 3-3a , 30167 Hannover , Germany
- Zentrum für Festkörperchemie und Neue Materialien (ZFM) , Leibniz Universität Hannover , Callinstr. 3-3a , 30167 Hannover , Germany
| | - Mazharul M. Islam
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie , Universität Bonn , Beringstr. 4 , 53115 Bonn , Germany
| | - Paul Heitjans
- Institut für Physikalische Chemie und Elektrochemie , Leibniz Universität Hannover , Callinstr. 3-3a , 30167 Hannover , Germany
- Zentrum für Festkörperchemie und Neue Materialien (ZFM) , Leibniz Universität Hannover , Callinstr. 3-3a , 30167 Hannover , Germany
| | - Thomas Bredow
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie , Universität Bonn , Beringstr. 4 , 53115 Bonn , Germany
| |
Collapse
|
3
|
Ding H, Xu B. Structural, elastic, and vibrational properties of layered titanium dichalcogenides: A van der Waals density functional study. J Chem Phys 2012; 137:224509. [DOI: 10.1063/1.4770293] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
|
5
|
Doublet ML, Gallego-Planas N, Philipsen PHT, Brec R, Jobic S. A new theoretical approach for the electrical properties of TiX2 (X=S, Se, Te) phases with density functional calculations. J Chem Phys 1998. [DOI: 10.1063/1.475426] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
6
|
Clerc DG, Poshusta RD, Hess AC. Periodic Hartree−Fock Study of LixTiS2, 0 ≤ x ≤ 1: The Structural, Elastic, and Electronic Effects of Lithium Intercalation in TiS2. J Phys Chem A 1997. [DOI: 10.1021/jp9618789] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- D. G. Clerc
- Materials Science Program, Washington State University, Pullman, Washington 99164-4630
| | - R. D. Poshusta
- Materials Science Program, Washington State University, Pullman, Washington 99164-4630
| | - A. C. Hess
- Environmental Molecular Sciences Laboratory, MS K1-90, Pacific Northwest Laboratory, Richland, Washington 99352
| |
Collapse
|