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<p>The development of efficient and environmentally friendly solid-state hydrogen storage materials remains a major challenge for clean energy technologies. In this study, the structural, electronic, mechanical, optical, vibrational, thermal, and hydrogen storage properties of K-doped Rb<sub>7</sub>KSn<sub>4</sub>H<sub>16</sub> were systematically investigated using first-principles density functional theory calculations. The compound was constructed by partial substitution of Rb with K in the parent Rb<sub>2</sub>SnH<sub>4</sub> structure to evaluate the effect of alkali-metal doping on hydrogen storage performance and physical properties. The calculated negative formation energy confirms thermodynamic stability, while the absence of imaginary phonon frequencies demonstrates dynamical stability. Electronic structure calculations reveal that Rb<sub>7</sub>KSn<sub>4</sub>H<sub>16</sub> is a direct band gap semiconductor with a band gap of 0.722&#xa0;eV. Mechanical analysis indicates brittle behavior with dominant covalent bonding characteristics. Optical results show enhanced low-energy reflectivity and optical conductivity after K substitution. Thermal calculations indicate robust lattice stability with heat capacity saturation near 140&#xa0;cal/mol&#xa0;K at elevated temperatures. The compound exhibits a gravimetric hydrogen storage capacity of approximately 2.88 wt%, demonstrating the potential of alkali-metal substitution for tuning complex hydrides. Although this value remains below the current U.S. DOE target for practical applications, the combined thermodynamic, mechanical, and dynamical stability highlights Rb<sub>7</sub>KSn<sub>4</sub>H<sub>16</sub> as a promising candidate for future solid-state hydrogen storage research.</p>

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First-principles investigation of K-doped Rb7KSn4H16 for hydrogen storage: a study of structural, electronic, mechanical, optical, dynamic, and thermal properties

  • 期刊论文

  • 发表日期：

    2026年7月5日

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  • Cihan Kürkçü,
  • Cengiz Soykan

摘要

The development of efficient and environmentally friendly solid-state hydrogen storage materials remains a major challenge for clean energy technologies. In this study, the structural, electronic, mechanical, optical, vibrational, thermal, and hydrogen storage properties of K-doped Rb7KSn4H16 were systematically investigated using first-principles density functional theory calculations. The compound was constructed by partial substitution of Rb with K in the parent Rb2SnH4 structure to evaluate the effect of alkali-metal doping on hydrogen storage performance and physical properties. The calculated negative formation energy confirms thermodynamic stability, while the absence of imaginary phonon frequencies demonstrates dynamical stability. Electronic structure calculations reveal that Rb7KSn4H16 is a direct band gap semiconductor with a band gap of 0.722 eV. Mechanical analysis indicates brittle behavior with dominant covalent bonding characteristics. Optical results show enhanced low-energy reflectivity and optical conductivity after K substitution. Thermal calculations indicate robust lattice stability with heat capacity saturation near 140 cal/mol K at elevated temperatures. The compound exhibits a gravimetric hydrogen storage capacity of approximately 2.88 wt%, demonstrating the potential of alkali-metal substitution for tuning complex hydrides. Although this value remains below the current U.S. DOE target for practical applications, the combined thermodynamic, mechanical, and dynamical stability highlights Rb7KSn4H16 as a promising candidate for future solid-state hydrogen storage research.