A-site cation engineering of lead-free M2NiCl6 (M = Na, K, Cs) vacancy-ordered double perovskites: first-principles insights into stability, band-gap tuning, excitonic behavior, and optical response
4 affiliations
- 1Department of Computer and Communication Engineering, International Islamic University Chittagong Kumira Chittagong 4318 Bangladesh
- 2Department of Physics, Comilla University Cumilla-3506 Bangladesh
- 3Department of Physics, College of Science, Umm Al-Qura University Makkah 21955 Saudi Arabia
- 4Materials Research and Simulation Lab, Department of Electrical and Electronic Engineering, International Islamic University Chittagong Kumira Chittagong 4318 Bangladesh
Abstract
The growing global energy demand and the environmental consequences of fossil-fuel consumption underscore the urgent need to develop sustainable, efficient, and environmentally benign energy materials. Lead-free vacancy-ordered double halide perovskites M2NiCl6 (M = Na, K, Cs) were systematically investigated using first-principles calculations to evaluate their structural stability, mechanical reliability, thermophysical behavior, electronic structure, and optical response. The optimized compounds crystallize in the cubic Fm3̄m phase with stable [NiCl6]2− octahedral frameworks. Negative formation and binding energies confirm their thermodynamic stability, while tolerance and octahedral factors support their structural feasibility. Elastic analysis verifies mechanical stability for all compounds, with K2NiCl6 showing ductile behavior and the highest fracture toughness, whereas Cs2NiCl6 exhibits superior stiffness, hardness, and dimensional stability. The low elastic moduli and thermal conductivities indicate mechanically soft and thermally insulating characteristics. Electronic band-structure calculations reveal indirect semiconducting behavior, with TB-mBJ band gaps of 1.883, 1.792, and 1.083 eV for Na2NiCl6, K2NiCl6, and Cs2NiCl6, respectively. PDOS analysis shows that Ni-3d and Cl-3p states dominate the band edges, while enhanced Cs-4p hybridization narrows the band gap. Strong visible-to-near-infrared absorption, low reflectivity, and tunable optical conductivity suggest promising potential for photovoltaic, photodetector, and optoelectronic applications.
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BibTeX
@article{mia2026asite,
title = {{A-site cation engineering of lead-free M2NiCl6 (M = Na, K, Cs) vacancy-ordered double perovskites: first-principles insights into stability, band-gap tuning, excitonic behavior, and optical response}},
author = {Md. Hasan Mia and Md. Abdul Momin and Arka Deb Nath and Fahad Alhashmi Alamer and Omar Alsalmi and Md. Rasheduzzaman and Md. Zahid Hasan},
journal = {RSC Advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra08772h},
url = {https://doi.org/10.1039/d6ra08772h},
note = {CC BY-NC 3.0},
}
RIS
TY - JOUR
TI - A-site cation engineering of lead-free M2NiCl6 (M = Na, K, Cs) vacancy-ordered double perovskites: first-principles insights into stability, band-gap tuning, excitonic behavior, and optical response
AU - Md. Hasan Mia
AU - Md. Abdul Momin
AU - Arka Deb Nath
AU - Fahad Alhashmi Alamer
AU - Omar Alsalmi
AU - Md. Rasheduzzaman
AU - Md. Zahid Hasan
PY - 2026
DA - 2026/10/09
JO - RSC Advances
DO - 10.1039/d6ra08772h
UR - https://doi.org/10.1039/d6ra08772h
AB - The growing global energy demand and the environmental consequences of fossil-fuel consumption underscore the urgent need to develop sustainable, efficient, and environmentally benign energy materials. Lead-free vacancy-ordered double halide perovskites M2NiCl6 (M = Na, K, Cs) were systematically investigated using first-principles calculations to evaluate their structural stability, mechanical reliability, thermophysical behavior, electronic structure, and optical response. The optimized compounds crystallize in the cubic Fm3̄m phase with stable [NiCl6]2− octahedral frameworks. Negative formation and binding energies confirm their thermodynamic stability, while tolerance and octahedral factors support their structural feasibility. Elastic analysis verifies mechanical stability for all compounds, with K2NiCl6 showing ductile behavior and the highest fracture toughness, whereas Cs2NiCl6 exhibits superior stiffness, hardness, and dimensional stability. The low elastic moduli and thermal conductivities indicate mechanically soft and thermally insulating characteristics. Electronic band-structure calculations reveal indirect semiconducting behavior, with TB-mBJ band gaps of 1.883, 1.792, and 1.083 eV for Na2NiCl6, K2NiCl6, and Cs2NiCl6, respectively. PDOS analysis shows that Ni-3d and Cl-3p states dominate the band edges, while enhanced Cs-4p hybridization narrows the band gap. Strong visible-to-near-infrared absorption, low reflectivity, and tunable optical conductivity suggest promising potential for photovoltaic, photodetector, and optoelectronic applications.
SN - 2046-2069
ER -