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
In order to reveal the mechanism of surface hydration differences for different types of montmorillonite crystals,the hydration processes of sodium,potassium,and calcium montmorillonite were simulated by molecular dyn...In order to reveal the mechanism of surface hydration differences for different types of montmorillonite crystals,the hydration processes of sodium,potassium,and calcium montmorillonite were simulated by molecular dynamics.These simulation results show that with the increase of the number of water molecules,the interlayer spacing of montmorillonite expands in a step-by-step manner,accompanied by volume expansion,decrease in density,and increase in self-diffusion coefficients of water molecules and cations.In addition,as the water molecular layer accumulates,the peak values of the radial distribution function between Na^(+)/K^(+)/Ca^(2+)ions and Ow/Hw(oxygen or hydrogen atoms in water molecules)gradually decrease.The degree of polymerization of water intensifies before decreasing,while the elastic modulus and acoustic velocity are gradually decreasing.It is worth noting that Na^(+)ion shows the highest tendency to hydrate,followed by Ca^(2+),and then K^(+).Among the cations studied,Ca^(2+)ion has the highest hydration coordination number,hydration number and hydration radius.As a result,calcium montmorillonite exhibits the widest intensity range and the largest acoustic velocity.These findings can provide references for engineering practices such as oil and gas exploration,tunnel excavation,slope stabilization,and deep geological disposal.展开更多
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.
基金Projects(52374080,41772151)supported by the National Natural Science Foundation of China。
文摘In order to reveal the mechanism of surface hydration differences for different types of montmorillonite crystals,the hydration processes of sodium,potassium,and calcium montmorillonite were simulated by molecular dynamics.These simulation results show that with the increase of the number of water molecules,the interlayer spacing of montmorillonite expands in a step-by-step manner,accompanied by volume expansion,decrease in density,and increase in self-diffusion coefficients of water molecules and cations.In addition,as the water molecular layer accumulates,the peak values of the radial distribution function between Na^(+)/K^(+)/Ca^(2+)ions and Ow/Hw(oxygen or hydrogen atoms in water molecules)gradually decrease.The degree of polymerization of water intensifies before decreasing,while the elastic modulus and acoustic velocity are gradually decreasing.It is worth noting that Na^(+)ion shows the highest tendency to hydrate,followed by Ca^(2+),and then K^(+).Among the cations studied,Ca^(2+)ion has the highest hydration coordination number,hydration number and hydration radius.As a result,calcium montmorillonite exhibits the widest intensity range and the largest acoustic velocity.These findings can provide references for engineering practices such as oil and gas exploration,tunnel excavation,slope stabilization,and deep geological disposal.
