Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-N...Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-NEB)method,we performed first-principles calculations of diffusion characteristics of helium in perfect aragonite crystal under high pressure to 40 GPa.Our results show that He diffusion behaviors are controlled by pressure,temperature and crystal size.The activation energy increases,and the diffusion coefficients decrease significantly under high pressure.Ea[100]increases from 176.02 kJ/mol to 278.75 kJ/mol,and Ea[001]increases from 195.89 kJ/mol to 290.43 kJ/mol,with pressure increasing from 20 GPa to 40 GPa.At 700 K,the diffusion coefficients at 40 GPa is 7 orders of magnitude lower than that at 20 GPa;and at 1000 K it decrease 5 orders of magnitude.To ensure that at least 90%helium is not lost,we synthesized the temperature obtained from cooling and heating processes and derive the'stable temperature range'for helium in aragonite.The obtained results show that the stable temperature range is 22-76℃at 0 GPa and 641-872℃at 40 GPa,for the crystal of 100-2000μm size.Besides,the travel time of helium in aragonite under high pressure increases rapidly with pressure increasing.Our calculations indicate that helium can be quantitatively retained in aragonite in the deep mantle as long as the temperature is in the'stable temperature range'.These results have certain implications for exploring the evolution of mantle and the storage of helium within it.展开更多
The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated ...The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated molecular dynamics simulations spanning broad temperature-pressure-composition(2000–10000 K, 1–7 Mbar,pure H to pure He) regimes, we systematically determine self and mutual diffusion coefficients in H–He systems and establish a six-dimensional framework correlating temperature, pressure, helium abundance, phase separation degree, diffusion coefficients, and anisotropy. Key findings reveal that hydrogen exhibits active directional migration with pronounced diffusion anisotropy, whereas helium passively aggregates in response. While the conventional mixing rule underestimates mutual diffusion coefficients by neglecting velocity cross-correlations,the assumption of an ideal thermodynamic factor(Q = 1) overestimates them due to unaccounted non-ideal thermodynamic effects—both particularly pronounced in strongly phase-separated regimes. Notably, hydrogen's dual role, anisotropic diffusion and bond stabilization via helium doping, modulates demixing kinetics. Large-scale simulations(216,000 atoms) propose novel phase-separation paradigms, such as “hydrogen bubble/wisp” formation, challenging the classical “helium rain” scenario, striving to bridge atomic-scale dynamics to planetary-scale phase evolution.展开更多
Diffusion behavior of helium in molybdenum was investigated by means of the in- ternal friction method. An apparent relaxation internal friction peak associated with helium long-range diffusion was observed around 475...Diffusion behavior of helium in molybdenum was investigated by means of the in- ternal friction method. An apparent relaxation internal friction peak associated with helium long-range diffusion was observed around 475 K at a resonant frequency of 56 Hz. In terms of the Gorsky relaxation model and the shift of the peak position with the measurement frequency, the activation energy and pre-exponential factor of the diffusion coefficient of the helium atoms in molybdenum were deduced as 0.63 eV and 6.5 cm2/s, respectively.展开更多
The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is cru...The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics（MD） simulation for the bulk hcp-Ti system and the system with grain boundary（GB）. It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic（the diffusion coefficient of the [0001] direction is higher than that of the basal plane）,as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary（TB） can serve as an effective trapped region for He.The TB accelerates diffusion of He in the direction perpendicular to the twinning direction（TD）, while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region.展开更多
Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential d...Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.42394114,41573121,42174115)Open Foundation of the United Laboratory of High-Pressure Physics and Earthquake Science(Grant No.2019HPPES06).
文摘Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle.Based on the density functional theory(DFT)and the the climbing image nudged elastic band(CI-NEB)method,we performed first-principles calculations of diffusion characteristics of helium in perfect aragonite crystal under high pressure to 40 GPa.Our results show that He diffusion behaviors are controlled by pressure,temperature and crystal size.The activation energy increases,and the diffusion coefficients decrease significantly under high pressure.Ea[100]increases from 176.02 kJ/mol to 278.75 kJ/mol,and Ea[001]increases from 195.89 kJ/mol to 290.43 kJ/mol,with pressure increasing from 20 GPa to 40 GPa.At 700 K,the diffusion coefficients at 40 GPa is 7 orders of magnitude lower than that at 20 GPa;and at 1000 K it decrease 5 orders of magnitude.To ensure that at least 90%helium is not lost,we synthesized the temperature obtained from cooling and heating processes and derive the'stable temperature range'for helium in aragonite.The obtained results show that the stable temperature range is 22-76℃at 0 GPa and 641-872℃at 40 GPa,for the crystal of 100-2000μm size.Besides,the travel time of helium in aragonite under high pressure increases rapidly with pressure increasing.Our calculations indicate that helium can be quantitatively retained in aragonite in the deep mantle as long as the temperature is in the'stable temperature range'.These results have certain implications for exploring the evolution of mantle and the storage of helium within it.
基金supported by the National University of Defense Technology Research Fund Projectthe National Natural Science Foundation of China under Grant Nos. 12047561 and 12104507+1 种基金the NSAF under Grant No. U1830206the Science and Technology Innovation Program of Hunan Province under Grant No. 2021RC4026。
文摘The dynamics of phase separation in H–He binary systems within gas giants such as Jupiter and Saturn exhibit remarkable complexity, yet lack systematic investigation. Through large-scale machine-learning-accelerated molecular dynamics simulations spanning broad temperature-pressure-composition(2000–10000 K, 1–7 Mbar,pure H to pure He) regimes, we systematically determine self and mutual diffusion coefficients in H–He systems and establish a six-dimensional framework correlating temperature, pressure, helium abundance, phase separation degree, diffusion coefficients, and anisotropy. Key findings reveal that hydrogen exhibits active directional migration with pronounced diffusion anisotropy, whereas helium passively aggregates in response. While the conventional mixing rule underestimates mutual diffusion coefficients by neglecting velocity cross-correlations,the assumption of an ideal thermodynamic factor(Q = 1) overestimates them due to unaccounted non-ideal thermodynamic effects—both particularly pronounced in strongly phase-separated regimes. Notably, hydrogen's dual role, anisotropic diffusion and bond stabilization via helium doping, modulates demixing kinetics. Large-scale simulations(216,000 atoms) propose novel phase-separation paradigms, such as “hydrogen bubble/wisp” formation, challenging the classical “helium rain” scenario, striving to bridge atomic-scale dynamics to planetary-scale phase evolution.
文摘Diffusion behavior of helium in molybdenum was investigated by means of the in- ternal friction method. An apparent relaxation internal friction peak associated with helium long-range diffusion was observed around 475 K at a resonant frequency of 56 Hz. In terms of the Gorsky relaxation model and the shift of the peak position with the measurement frequency, the activation energy and pre-exponential factor of the diffusion coefficient of the helium atoms in molybdenum were deduced as 0.63 eV and 6.5 cm2/s, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant No.51501119)the Scientific Research Starting Foundation for Younger Teachers of Sichuan University,China(Grant No.2015SCU11058)+1 种基金the National Magnetic Confinement Fusion Science Program of China(Grant No.2013GB109002)the Cooperative Research Project "Research of Diffusion Behaviour of He in Grain Boundary of HCP-Titanium",China
文摘The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics（MD） simulation for the bulk hcp-Ti system and the system with grain boundary（GB）. It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic（the diffusion coefficient of the [0001] direction is higher than that of the basal plane）,as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary（TB） can serve as an effective trapped region for He.The TB accelerates diffusion of He in the direction perpendicular to the twinning direction（TD）, while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region.
基金supported by the National Basic Research and Development Program of China(Grant Nos.2010CB832904 and 2010CB832902)the National Natural Science Foundation of China(Grant No.91226202)
文摘Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.
