Few-Layer PdSe2 Sheets: Promising Thermoelectric Materials Driven by High Valley Convergence

Minglei Sun; Jyh-Pin Chou; Lihong Shi; Junfeng Gao; Alice Hu; Wencheng Tang; Gang Zhang

doi:10.1021/acsomega.8b00485

Few-Layer PdSe₂ Sheets: Promising Thermoelectric Materials Driven by High Valley Convergence

ACS Omega. 2018 Jun 4;3(6):5971-5979. doi: 10.1021/acsomega.8b00485. eCollection 2018 Jun 30.

Authors

Minglei Sun^{1

2}, Jyh-Pin Chou³, Lihong Shi⁴, Junfeng Gao², Alice Hu³, Wencheng Tang¹, Gang Zhang²

Affiliations

¹ School of Mechanical Engineering, Southeast University, 79 Suyuan Avenue, Nanjing 211189, China.
² Institute of High Performance Computing, ASTAR, 1 Fusionopolis Way, Singapore 138632, Singapore.
³ Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong 999077, China.
⁴ School of Science, JiangNan University, 1800 Lihu Avenue, Wuxi 214122, China.

Abstract

Herein, we report a comprehensive study on the structural and electronic properties of bulk, monolayer, and multilayer PdSe₂ sheets. First, we present a benchmark study on the structural properties of bulk PdSe₂ by using 13 commonly used density functional theory (DFT) functionals. Unexpectedly, the most commonly used van der Waals (vdW)-correction methods, including DFT-D2, optB88, and vdW-DF2, fail to provide accurate predictions of lattice parameters compared to experimental data (relative error > 15%). On the other hand, the PBE-TS series functionals provide significantly improved prediction with a relative error of <2%. Unlike hexagonal two-dimensional materials like graphene, transition metal dichalcogenides, and h-BN, the conduction band minimum of monolayer PdSe₂ is not located along the high symmetry lines in the first Brillouin zone; this highlights the importance of the structure-property relationship in the pentagonal lattice. Interestingly, high valley convergence is found in the conduction and valence bands in monolayer, bilayer, and trilayer PdSe₂ sheets, suggesting promising application in thermoelectric cooling.