Related Experiment Video
Updated: Dec 3, 2025
Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
Published on: October 12, 2019
Negative Poisson Ratio in Two-Dimensional Tungsten Nitride: Synergistic Effect from Electronic and Structural
Wenyuan Jin1, Weiguo Sun1, Xiaoyu Kuang1
1Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
Abstract:
Low-dimensional materials with high stabilities and outstanding mechanical properties are essential for next generation microelectromechanical systems (MEMS). The successful synthesis of two-dimensional (2D) tungsten nitride makes it a promising candidate for the MEMS application. Here, we have confirmed the existence of experimentally synthesized W2N3 and predicted three additional new 2D monolayer tungsten nitrides: WN2, WN4, and W3N based on extensively structural searches by CALYPSO method and first-principle calculations. The calculations indicate that the nitrogen-rich WN4 monolayer possesses large in-plane negative Poisson ratios attributed to the 4-fold-coordinated WN4 ν = -0.103 and ν = -0.113, which are tetrahedron combined with the strong coupling between the 2p orbitals of N and 5d orbitals of W. Our findings not only enrich the family of 2D transition metal nitrides with excellent mechanical properties but also open avenues for design and synthesis of other novel 2D layered materials.
Related Concept Videos
01:23Poisson's Ratio
01:11P-N junction
01:20Types of Semiconductors
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...