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Updated: Nov 30, 2025
Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
Published on: October 12, 2019
Perspectives on van der Waals Density Functionals: The Case of TiS2
Jaron T Krogel1,2, Simuck F Yuk1, Paul R C Kent2
1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Accurate van der Waals density functionals are crucial for modeling 2D nanomaterials. New vdW-DF variants improve binding energy and interlayer distance predictions for TiS2, though LDA and PBEsol better capture electron density responses.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Chemistry
Background:
- Van der Waals (vdW) interactions are fundamental to layered 2D nanomaterials and their device applications.
- Van der Waals density functionals (vdW-DFs) are widely used for first-principles calculations of these systems.
- Existing vdW-DFs require refinement for accurate microscopic descriptions of vdW forces.
Purpose of the Study:
- To compute benchmark binding energies and electronic density responses for TiS2 using diffusion quantum Monte Carlo (DMC).
- To evaluate the performance of various vdW-DFs against DMC benchmarks.
- To identify improved functionals for describing vdW interactions in 2D materials.
Main Methods:
- Diffusion Quantum Monte Carlo (DMC) calculations for benchmark data.
- Comparison of DMC results with local, semilocal, and various vdW-DFs (vdW-DF, vdW-DF2, vdW-DF-C09, vdW-DF-optB88, vdW-DF-optB86b, vdW-DF2-B86R).
- Analysis of binding energy, interlayer separation, and electronic density response.
Main Results:
- A strong correlation exists between accurate interlayer separation and binding energy predictions for TiS2.
- The vdW-DF-optB88 functional demonstrated excellent performance for both interlayer distance and binding energy.
- More recent vdW-DF functionals generally show systematic improvements over older versions.
- Local-density approximation (LDA) and PBEsol outperformed vdW-DFs in describing interlayer charge accumulation, with vdW-DF-C09 variants showing the best performance among vdW-DFs.
Conclusions:
- The vdW-DF-optB88 functional is a promising candidate for accurate modeling of TiS2 interlayer properties.
- While vdW-DFs have improved, LDA and PBEsol remain competitive for describing electronic density responses in vdW-bound systems.
- Further development of vdW-DFs is needed to fully capture the electronic behavior associated with vdW binding.
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