DFT分子动力学：耦合过程与量子浓缩
Finite-temperature orbital-free DFT molecular dynamics: coupling Profess and Quantum Espresso
摘要：
实现轨道自由能泛函的专业代码和耦合的专业与量子咖啡代码进行说明。这种结合使得无轨道DFT能够在相同的基础上（算法、恒温器、收敛参数等）驱动从头计算分子动力学模拟。对于Kohn-Sham（KS）DFT。所有实现的非相互作用自由能泛函都是单点的：局域密度近似（LDA;也称为有限T梯度-费米，ftTF），二阶梯度近似（SGA或有限T梯度校正TF），以及我们最近引入的有限T广义梯度近似（ftGGA）。通过无轨道方法消除KS轨道瓶颈使得在普通计算机上进行高T模拟成为可能，而对于KS分子动力学（MD）来说，在非常高性能的计算机系统上进行这些模拟将是昂贵的甚至是非常耗时的。报告了在2，000 K <= T <= 4，000，000 K的温度范围内对H进行的示例MD模拟，时间为小型集群（16-128个核心）甚至笔记本电脑。相对于KS驱动的计算，无轨道计算的速度在几倍到几百倍之间。
英文摘要：
Implementation of orbital-free free-energy functionals in the Profess code and the coupling of Profess with the Quantum Espresso code are described. The combination enables orbital-free DFT to drive ab initio molecular dynamics simulations on the same footing (algorithms, thermostats, convergence parameters, etc.) as for Kohn-Sham (KS) DFT. All the non-interacting free-energy functionals implemented are single-point: the local density approximation (LDA; also known as finite-T Thomas-Fermi, ftTF), the second-order gradient approximation (SGA or finite-T gradient-corrected TF), and our recently introduced finite-T generalized gradient approximations (ftGGA). Elimination of the KS orbital bottleneck via orbital-free methodology enables high-T simulations on ordinary computers, whereas those simulations would be costly or even prohibitively time-consuming for KS molecular dynamics (MD) on very high-performance computer systems. Example MD simulations on H over a temperature range 2,000 K <= T <=4,000,000 K are reported, with timings on small clusters (16-128 cores) and even laptops. With respect to KS-driven calculations, the orbital-free calculations are between a few times through a few hundreds of times faster.
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