From Phosphate Fluoride to Fluorophosphate: Design of Novel Ultraviolet/Deep-Ultraviolet Nonlinear Optical Materials for BePO3F with Optical Property Enhancement

Mengfan Wu; Junwei Feng; Congwei Xie; Abudukadi Tudi; Dongdong Chu; Juanjuan Lu; Shilie Pan; Zhihua Yang

doi:10.1021/acsami.2c12001

From Phosphate Fluoride to Fluorophosphate: Design of Novel Ultraviolet/Deep-Ultraviolet Nonlinear Optical Materials for BePO₃F with Optical Property Enhancement

ACS Appl Mater Interfaces. 2022 Aug 31;14(34):39081-39090. doi: 10.1021/acsami.2c12001. Epub 2022 Aug 18.

Authors

Mengfan Wu^{1

2}, Junwei Feng¹, Congwei Xie¹, Abudukadi Tudi^{1

2}, Dongdong Chu^{1

2}, Juanjuan Lu¹, Shilie Pan^{1

2}, Zhihua Yang^{1

2}

Affiliations

¹ Research Center for Crystal Materials; CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Science, 40-1 South Beijing Road, Urumqi 830011, China.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 35980008
DOI: 10.1021/acsami.2c12001

Abstract

Fluorine-containing compounds have stimulated the exploration of ultraviolet/deep-ultraviolet nonlinear optical (NLO) materials. Alkali/alkaline-earth metal phosphates are one of the important potential systems as NLO materials, while the common small birefringence limits the phase-matching (PM) ability in the ultraviolet/deep-ultraviolet region. Herein, by applying a "fluorination synergy-induced enhancement of optical property" strategy, novel structures of phosphate fluoride/fluorophosphate in BePO₃F with good thermodynamic/dynamic stability and promising NLO-related properties are discovered via performing crystal structure prediction combined with first-principles calculations. BePO₃F-I-VI exhibit relatively large birefringence of 0.025, 0.048, 0.049, 0.049, 0.059, and 0.063 at 1064 nm, respectively. Simultaneously, BePO₃F-I (Pc) is a new thermodynamically stable phosphate fluoride which possesses a wide band gap (E_g = 8.03 eV), large second-harmonic generation (SHG) coefficient (d₁₁ = 0.67 pm/V, 1.7 × KDP), and the shortest PM wavelength of 292 nm. Other five thermodynamically metastable noncentrosymmetric (NCS) BePO₃F structures (II-VI) belong to fluorophosphates and exhibit deep-ultraviolet PM wavelengths of 187, 183, 186, 188, and 196 nm. It reveals that the aligned nonbonding O 2p orbitals of [BeO₂F₂] and [PO₄] units lead to a large SHG coefficient in the phosphate fluoride BePO₃F-I. For fluorophosphates (BePO₃F-II-VI), the synergy of [BeO₃] planar units and [PO₃F] units induces relatively large birefringence. Our research results provide an idea for exploring novel high-performance NLO materials.

Keywords: birefringence; crystal structure prediction; first-principles calculations; nonlinear optical materials; phosphates; second-harmonic generation; ultraviolet/deep-ultraviolet.