<p>To realize a hydrogen energy-based society, an efficient solid-state hydrogen-storage material is crucial. Among candidate materials, the storage performance and thermal management during the hydrogenation–dehydrogenation processes need to be improved by optimizing the thermofluid dynamics and thermal conductivity. A common approach is to add a thermally conductive material; however, few studies have tried to enhance the intrinsic thermal conductivity of solid-state hydrogen-storage materials because of their many crystalline phases depending on the temperature, pressure, and hydrogen concentration. We employed a first-principles anharmonic lattice dynamics to calculate the lattice thermal conductivity of the solid-state hydrogen-storage material Mg<InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq1.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>NiH<InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq2.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>4</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> considering various structures that correspond to the unresolved crystalline phases observed in previous high-pressure experiments. Our results revealed that the thermal conductivity of Mg<InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq1.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>NiH<InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq2.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>4</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation> has a non-trivial dependence on pressure that is driven by complex modulations of the vibrational characteristics. Moreover, the room-temperature thermal conductivities of the crystalline phases are below 20 W&#xa0;m<InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq9.gif" Format="GIF" Height="11" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation> K<InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq9.gif" Format="GIF" Height="11" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation> at pressures below 10&#xa0;GPa, which was attributed to the large mass contrast of constituent elements and the structural complexity. These findings provide valuable insights for the thermal engineering of hydrogen-storage units based on Mg<InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq1.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>2</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>NiH<InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10765_2025_3587_Article_IEq2.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="8" /> </InlineMediaObject> <EquationSource Format="TEX">\(_{4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>4</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>.</p>

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Intrinsic Thermal Conductivity of Mg\(_{2}\)NiH\(_{4}\) at High Pressures: A First-Principles Study

  • Takuma Shiga,
  • Takashi Yagi,
  • Hiroshi Fujihisa

摘要

To realize a hydrogen energy-based society, an efficient solid-state hydrogen-storage material is crucial. Among candidate materials, the storage performance and thermal management during the hydrogenation–dehydrogenation processes need to be improved by optimizing the thermofluid dynamics and thermal conductivity. A common approach is to add a thermally conductive material; however, few studies have tried to enhance the intrinsic thermal conductivity of solid-state hydrogen-storage materials because of their many crystalline phases depending on the temperature, pressure, and hydrogen concentration. We employed a first-principles anharmonic lattice dynamics to calculate the lattice thermal conductivity of the solid-state hydrogen-storage material Mg \(_{2}\) 2 NiH \(_{4}\) 4 considering various structures that correspond to the unresolved crystalline phases observed in previous high-pressure experiments. Our results revealed that the thermal conductivity of Mg \(_{2}\) 2 NiH \(_{4}\) 4 has a non-trivial dependence on pressure that is driven by complex modulations of the vibrational characteristics. Moreover, the room-temperature thermal conductivities of the crystalline phases are below 20 W m \(^{-1}\) - 1 K \(^{-1}\) - 1 at pressures below 10 GPa, which was attributed to the large mass contrast of constituent elements and the structural complexity. These findings provide valuable insights for the thermal engineering of hydrogen-storage units based on Mg \(_{2}\) 2 NiH \(_{4}\) 4 .