在正则系综统下,温度为2000 K时,利用基于密度泛函理论的第一性原理分子动力学计算方法对Al与赤铁矿α-Fe2O3的铝热反应进行了研究.模拟得出Fe—O键的数量随着时间的增加而减小,Al—O键和Fe—Fe键的数量随时间的增加而增大;同时Fe离子总的电荷量随时间的增加而减小,而Al离子总的电荷量随时间的增加而增大.模拟结果表明,在Al/Fe2O3铝热反应中发生了氧化还原反应,Al被氧化,Fe离子被还原;在界面处生成Al—O键,Fe—O键发生断裂;氧化还原反应完成需约3 ps.
Ab initio calculations of lattice constants, lattice stabilities of HgX(X = S, Se, Te) at different electronic temperatures(T_e) have been performed within the density functional theory(DFT). We find that the lattice constants of HgX increase and the phonon frequencies reduce as T_e increases. Especially the transverse-acoustic(TA) phonon frequencies of HgX gradually become negative with the elevation of the electron temperature. That is to say ultrafast intense laser induces lattice instabilities of HgX and athermal melting appears for the increase of laser intensity. What is more, with the X atom number increasing, the critical electronic temperatures of HgX are decreased in sequence. This result would be helpful for understanding the athermal melting processes for femtosecond laser micromachining.
We investigate the elastic and thermodynamic properties of nanolaminate V2 AlC by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, differing with the other four C11 , C12 , C13 and C33 constants. The Poisson's ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B/C44 investigations revealed that V2 AlC is brittle and the brittleness decreases with pressure. Also, we found that V2 AlC is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grüneisen parameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.
YANG ZeJinLIU QiangLI JinWANG ZhaoGUO AiMinLINGHU RongFengCHENG XinLuYANG XiangDong
Based on the similarity in models of the early Sun and the 3-D common focal region of the micro-pinch in X-pinch experiments, a novel hybrid fusion configuration by continuous focusing of multiple Z-pinched plasma beams on spatially symmetric plasma is proposed. By replacing gravity with Lorentz force with subsequent centripetal spherical pinch, the beamtarget fusion reactivity is enhanced in a quasi-spherical converging region, thus achieving MICF. An assessment, presented here, suggests that a practical fusion power source could be achieved using deuterium alone. Plasma instabilities can be suppressed by fast rotation resulting from an asymmetric tangential torsion in the spherical focal region of this configuration.Mathematical equivalence with the Sun allows the development of appropriate equations for the focal region of MICF, which are solved numerically to provide density, temperature and pressure distributions that produce net fusion energy output. An analysis of MICF physics and a preliminary experimental demonstration of a single beam are also carried out.
