Lone-Pair Electrons Do Not Necessarily Lead to Low Lattice Thermal Conductivity: An Exception of Two-Dimensional Penta-CN2

Huimin Wang; Guangzhao Qin; Zhenzhen Qin; Guojian Li; Qiang Wang; Ming Hu

doi:10.1021/acs.jpclett.8b00820

Lone-Pair Electrons Do Not Necessarily Lead to Low Lattice Thermal Conductivity: An Exception of Two-Dimensional Penta-CN₂

J Phys Chem Lett. 2018 May 17;9(10):2474-2483. doi: 10.1021/acs.jpclett.8b00820. Epub 2018 Apr 27.

Authors

Huimin Wang^{1

2}, Guangzhao Qin², Zhenzhen Qin³, Guojian Li¹, Qiang Wang¹, Ming Hu⁴

Affiliations

¹ Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education) , Northeastern University , 110819 Shenyang , China.
² Institute of Mineral Engineering, Division of Material Science and Engineering, Faculty of Georesources and Materials Engineering , RWTH Aachen University , 52064 Aachen , Germany.
³ Aachen Institute for Advanced Study in Computational Engineering Science (AICES) , RWTH Aachen University , 52062 Aachen , Germany.
⁴ Department of Mechanical Engineering , University of South Carolina , Columbia , South Carolina 29208 , United States.

PMID: 29692169
DOI: 10.1021/acs.jpclett.8b00820

Abstract

It has long been documented in the literature that lone-pair electrons (LPE) are generally thought to lead to low lattice thermal conductivity (κ_L) of bulk materials by inducing strong phonon anharmonicity. Herein, we show an exceptional case of two-dimensional (2D) penta-CN₂ that possesses LPE but exhibits more than doubled κ_L (660.71 W m^-1 K^-1) than the LPE free counterpart of penta-graphene (252.95 W m^-1 K^-1), which is unexpected and contradictory to the traditional theory of LPE leading to low κ_L. Based on the comparative study of four 2D systems possessing LPE and their respective LPE free counterparts (planar C₃N vs graphene and penta-CN₂ vs penta-graphene), the underlying mechanism is found lying in the bonds homogenization in penta-CN₂ due to the wide spatial extension of the nonsymmetrically distributed LPE, which compensates the lattice anharmonicity due to LPE and is responsible for the opposite tendency of LPE-affected κ_L in the four 2D systems.