Molecular dynamics simulations of shock response for nano-structure foamed gold
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摘要: 采用分子动力学计算程序对纳米结构泡沫金(Au)的冲击响应进行了模拟，得到了不同疏松度条件下泡沫Au的冲击压缩特性。通过获取不同势函数条件下实密Au的冲击Hugoniot关系以及泡沫结构稳定性测试选取适合描述Au泡沫冲击过程中原子的相互作用势。采用密堆积球壳的方式建立泡沫Au的初始构型。通过改变空心球壳的尺寸得到不同疏松度的稳定的泡沫Au结构。对泡沫Au的冲击过程进行分子动力学模拟，获得了不同疏松度泡沫Au在不同冲击压缩强度下的热力学状态参数。将模拟结果与已有的状态方程数据库以及疏松物质冲击压缩模型进行比较，结果表明，计算和理论模型给出的结果仍然存在明显的差异性，亟需通过进一步实验研究来验证模拟计算和理论模型结果的可靠性。
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关键词:
- 纳米Au结构稳定性 /
- Au泡沫 /
- 分子动力学模拟 /
- 泡沫冲击Hugoniot曲线
Abstract: Different embeded-atom method potentials of gold were used in molecular dynamics simulation for shocked solid gold. Comparison between the simulation results and the experiment data of Hugoniot state for gold has been carried out. The potentials whose corresponding simulating shocked Hugoniot data are consistent with theoretical prediction were used in subsequent foamed gold simulations. The initial configuration of foamed gold has been constructed by means of randomly accumulating sphere shells in the simulation box. Three kinds of configuration have been obtained via changing the thickness, outer-radius of the sphere shell and potentials. Hugoniot states of porous polycrystal gold with 3-dimensional nanostructure under shock compression have been simulated by means of molecular dynamics(MD) method. Comparison between simulated results with porous equation of state(EOS) model and existing EOS database for Au has been done. The discrepancy suggests that experiments for the state of porous gold are necessary to verify the theory and the simulation method for porous gold. -
图 1 不同Au原子EAM势函数模拟实密Au冲击Hugoniot关系与实验拟合曲线对比
Figure 1. Comparison between theory experiment fitting curve and simulated shock Hugoniot curve for solid gold by using different embedded atom method(EAM) potentials
图 2 不同初始原子构型分子动力学弛豫后结果(YZ平面)。其中(a)为Olsson势函数弛豫后的构型，(b-e)为Zhakhovskii势函数弛豫后的构型
Figure 2. Nano-structure after energy minimization (view of YZ-plane). Image (a) is the energy minimization result by using Olsson potential, while images (b-e) is the results by using Zhakhovskii potential
图 3 泡沫Au的冲击Hugoniot分子动力学模拟结果与QEOS和SESAME的对比
Figure 3. Comparison between shock Hugoniot simulation for foamed Au with QEOS and SESAME data
图 4 模拟结果与Geng HY模型预测曲线的对比
Figure 4. Comparison between simulation results and prediction values by Geng HY model
表 1 泡沫Au模型的参数表
Table 1. Parameters of foamed gold for shock response simulation
initial thickness of shell d/nm initial outer-radius of shell D0/nm porosity/m atom numbers simulation box size nm 1.3 8 2.146 2 429 272 1777 nm×222 nm×222 nm 1.3 16 3.678 5 671 490 2701 nm×360 nm×360 nm 1.3 20 4.385 7 445 416 2702 nm×450 nm×450 nm 
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