Hexagonal to Monoclinic Phase Transition in Dense Hydrogen Phase III Detected by High-Pressure NMR
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866909272111054848 |
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| author | Yang, Meng Zhou, Yishan Jana, Rajesh Nakagawa, Takeshi Fu, Yunhua Meier, Thomas |
| author_facet | Yang, Meng Zhou, Yishan Jana, Rajesh Nakagawa, Takeshi Fu, Yunhua Meier, Thomas |
| contents | Conclusive crystal structure determination of the high pressure phases of hydrogen remains elusive due to lack of core electrons and vanishing wave vectors, rendering standard high-pressure experimental methods moot. Ab-initio DFT calculations have shown that structural polymorphism might be solely resolvable using high-resolution nuclear magnetic resonance (NMR) spectroscopy at mega-bar pressures, however technical challenges have precluded such experiments thus far. Here, we present in-situ high-pressure high-resolution NMR experiments in hydrogen phase III between 181 GPa and 208 GPa at room temperature. Our spectra suggest that at lower pressures phase III adopts a hexagonal P6122 crystal structure, transitioning into a monoclinic C2/c phase at about 197 GPa. The high resolution spectra are in excellent agreement with earlier structural and spectral predictions and underline the possibility of a subtle P6122 to C2/c phase transition in hydrogen phase III. These experiments show the importance of a combination of ab-initio calculations and low-Z sensitive spectral probes in high-pressure science in elucidating the structural complexity of the most abundant element in our universe. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2407_19368 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Hexagonal to Monoclinic Phase Transition in Dense Hydrogen Phase III Detected by High-Pressure NMR Yang, Meng Zhou, Yishan Jana, Rajesh Nakagawa, Takeshi Fu, Yunhua Meier, Thomas Materials Science Conclusive crystal structure determination of the high pressure phases of hydrogen remains elusive due to lack of core electrons and vanishing wave vectors, rendering standard high-pressure experimental methods moot. Ab-initio DFT calculations have shown that structural polymorphism might be solely resolvable using high-resolution nuclear magnetic resonance (NMR) spectroscopy at mega-bar pressures, however technical challenges have precluded such experiments thus far. Here, we present in-situ high-pressure high-resolution NMR experiments in hydrogen phase III between 181 GPa and 208 GPa at room temperature. Our spectra suggest that at lower pressures phase III adopts a hexagonal P6122 crystal structure, transitioning into a monoclinic C2/c phase at about 197 GPa. The high resolution spectra are in excellent agreement with earlier structural and spectral predictions and underline the possibility of a subtle P6122 to C2/c phase transition in hydrogen phase III. These experiments show the importance of a combination of ab-initio calculations and low-Z sensitive spectral probes in high-pressure science in elucidating the structural complexity of the most abundant element in our universe. |
| title | Hexagonal to Monoclinic Phase Transition in Dense Hydrogen Phase III Detected by High-Pressure NMR |
| topic | Materials Science |
| url | https://arxiv.org/abs/2407.19368 |