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Development of efficient molecular simulation techniques for engineering applications.

机译：开发用于工程应用的高效分子模拟技术。

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Engineering Molecular Mechanics (EMM) was developed as an alternative to conventional molecular simulation techniques to model high temperature ( T > 0 K ) phenomena. The EMM methodology was developed using thermal expansion and thermal energy as key thermal properties. Temperature dependent interatomic potentials were developed to account for thermal effects. Lennard-Jones and Morse potentials were used to build temperature dependent potentials. The validity and effectiveness of EMM simulations were demonstrated by simulating temperature dependent properties such as thermal expansion, elastic constants and thermal stress in copper and nickel. EMM simulations were significantly faster than molecular dynamics (MD) simulations for the same accuracy. A controversy regarding the definition of stress in an atomic system was resolved. Using theoretical arguments and numerical examples, the equivalence of virial stress and Cauchy stress was proved. It was shown that neglecting the velocity term in the definition of virial stress (as suggested by some researchers) can cause significant errors in MD simulations at high temperatures. The nanoscale instabilities during phase transformation in Ni-Al shape memory alloys were studied using MD and EMM simulations. The phase transformation temperatures predicted by MD simulations agreed well with experiments. Some limitations of the EMM methodology and the minimization algorithm were discussed. The possibility of nanoscale material design of Ni-Al shape memory alloys was investigated. It was found that the distribution of nickel and aluminum atoms in the alloy can affect the phase transformation characteristics significantly. A new design criterion based on thermal expansion mismatch was introduced. The predicted results using the new criterion matched well with the phase transformation temperature and strain calculated using MD simulations. The new one parameter design criterion was shown to be effective for designing Ni-Al shape memory alloys.
机译：开发了工程分子力学（EMM），以替代传统分子模拟技术来模拟高温（T> 0 K）现象。 EMM方法是使用热膨胀和热能作为关键的热性能而开发的。开发了温度依赖性原子间电势以解释热效应。 Lennard-Jones和莫尔斯电势被用来建立与温度相关的电势。通过模拟温度相关属性（例如铜和镍中的热膨胀，弹性常数和热应力）证明了EMM仿真的有效性和有效性。对于相同的精度，EMM仿真要比分子动力学（MD）仿真快得多。解决了有关原子系统中应力定义的争议。使用理论论证和数值例子，证明了病毒性应力和柯西应力的等效性。结果表明，忽略病毒应力定义中的速度项（如一些研究人员所建议的那样）会在高温下的MD模拟中引起重大错误。使用MD和EMM模拟研究了Ni-Al形状记忆合金在相变过程中的纳米级不稳定性。 MD模拟预测的相变温度与实验吻合良好。讨论了EMM方法和最小化算法的一些局限性。研究了Ni-Al形状记忆合金纳米材料设计的可能性。发现合金中镍和铝原子的分布会显着影响相变特性。介绍了一种基于热膨胀失配的新设计准则。使用新标准的预测结果与使用MD模拟计算的相变温度和应变非常匹配。新的一参数设计准则被证明对于设计Ni-Al形状记忆合金是有效的。

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