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Unveiling vibrational and optoelectronic properties of HfX2 (X = Br, I) monolayers via DFT calculations.

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Title: Unveiling vibrational and optoelectronic properties of HfX2 (X = Br, I) monolayers via DFT calculations.
Authors: Santos, W. O.1, Barbosa, L. S.2, Moreira, E.3 edvan.moreira@fisica.uema.br, Azevedo, D. L.4
Source: Journal of Applied Physics. 9/14/2025, Vol. 138 Issue 10, p1-10. 10p.
Subject Terms: *OPTOELECTRONICS, *MONOMOLECULAR films, *DENSITY functional theory, *TRANSITION metal compounds, *QUANTUM theory, *FIELD-effect transistors, *BAND gaps
Abstract: The optoelectronic properties, phonon dispersion, stability, and quantum dynamics of HfX 2 -type transition-metal dihalides (TMDHs) were systematically investigated using first-principles calculations based on Density Functional Theory (DFT) with GGA-PBE and HSE06 functionals. Both HfBr 2 and HfI 2 monolayers exhibit structural stability, as indicated by phonon dispersion studies showing no negative frequencies, while cohesive energy and dynamic analysis confirm their energetic stability. Infrared (IR) and Raman spectra were calculated, assigned, and compared. The electronic properties of TMDHs reveal close direct and indirect bandgaps, with HfBr 2 having a direct bandgap of 1.33 eV (HSE06) and an indirect bandgap of 1.19 eV (HSE06), and HfI 2 displaying a direct bandgap of 1.04 eV (HSE06) and an indirect bandgap of 0.90 eV (HSE06), suggesting potential applications in field-effect transistors (FETs). These bandgap values are consistent with the experimental bandgap values of 2D and bulk HfSe 2. The spectroscopic limited maximum efficiency method was used to estimate power conversion efficiency for both HfX 2 -type monolayers. Electronic excitations occur in the ultraviolet region of the electromagnetic spectrum, implying that HfX 2 monolayers can serve as effective ultraviolet filters for polarized light. The calculations show that the HfBr 2 and HfI 2 monolayers are feasible and hold promise for various technological applications. [ABSTRACT FROM AUTHOR]
Database: Academic Search Index
Description
Abstract:The optoelectronic properties, phonon dispersion, stability, and quantum dynamics of HfX 2 -type transition-metal dihalides (TMDHs) were systematically investigated using first-principles calculations based on Density Functional Theory (DFT) with GGA-PBE and HSE06 functionals. Both HfBr 2 and HfI 2 monolayers exhibit structural stability, as indicated by phonon dispersion studies showing no negative frequencies, while cohesive energy and dynamic analysis confirm their energetic stability. Infrared (IR) and Raman spectra were calculated, assigned, and compared. The electronic properties of TMDHs reveal close direct and indirect bandgaps, with HfBr 2 having a direct bandgap of 1.33 eV (HSE06) and an indirect bandgap of 1.19 eV (HSE06), and HfI 2 displaying a direct bandgap of 1.04 eV (HSE06) and an indirect bandgap of 0.90 eV (HSE06), suggesting potential applications in field-effect transistors (FETs). These bandgap values are consistent with the experimental bandgap values of 2D and bulk HfSe 2. The spectroscopic limited maximum efficiency method was used to estimate power conversion efficiency for both HfX 2 -type monolayers. Electronic excitations occur in the ultraviolet region of the electromagnetic spectrum, implying that HfX 2 monolayers can serve as effective ultraviolet filters for polarized light. The calculations show that the HfBr 2 and HfI 2 monolayers are feasible and hold promise for various technological applications. [ABSTRACT FROM AUTHOR]
ISSN:00218979
DOI:10.1063/5.0286460