Ab-initio Quantum Monte Carlo Simulations of Warm Dense Matter

本项目主要研究热致密物质(WDM)的热力学和输运性质，WDM是固体和等离子体交界处的一种奇异状态。WDM对于理解天体(巨行星、矮星等)至关重要。对于极端压力或高激发下的物质也是如此。近年来，在自由电子激光设备中进行实验研究时，这种状态变得容易获得，新的诊断方法使精确分析成为可能。这对理论和仿真都提出了挑战。然而，WDM的复杂属性--强关联、电子量子效应、部分电离和有限的温度--只能进行定性描述。密度泛函理论(DFT)的使用使这一领域取得了重大进展，但DFT需要有关有限温度下电子的交换关联自由能FXC的信息。在这个项目的第一阶段，我们可以解决这个问题。我们发展了一种新的路径积分蒙特卡罗(PIMC)模拟方法--置换阻塞PIMC(PB-PIMC)，它使我们能够精确地计算电子的热力学性质。本提案的目的是继续发展这些情况。我们计划将模拟扩展到巨正则系综和附加观测的计算，包括输运性质、松原格林函数和谱函数。最后，我们计划将模拟扩展到波分复用条件下的氢气。预期结果的高精确度将使我们能够验证来自早期模型和模拟的数据，并最终建议对这些方法进行改进。此外，我们将能够对实验做出准确的预测。

This project focuses on the thermodynamic and transport properties of warm dense matter (WDM) – an exotic state on the boarder between solid and plasma. WDM is of fundamental importance for understanding astrophysical objects (giant planets, dwarf stars etc.) as well as for matter under extreme pressure or high excitation. In recent years such states became accessible for experimental investigation in free electron laser facilities, and new diagnostics enabled precise analysis. This poses a challenge to theory and simulation. However, the complex properties of WDM – strong correlations, electronic quantum effects, partial ionization and finite temperatures – allow only for a qualitative description. The use of density functional theory (DFT) has allowed for significant progress in this field, but DFT requires information about the exchange correlation free energy, fXC , of the electrons at finite temperature. In the first phase of this project we could solve this problem. We developed a new path integral Monte Carlo (PIMC) simulation method – permutation blocking PIMC (PB-PIMC) – which allowed us to compute the thermodynamic properties of the electrons exactly. The present proposal aims at continuation of these developments. We plan to extend the simulations to the grand canonical ensemble and to the computation of additional observables, including transport properties, the Matsubara Green function, and the spectral function. Finally, we plan to extend the simulations to hydrogen under WDM conditions. The expected high accuracy of the results will allow us to verify data from earlier models and simulations and, eventually suggest improvements of those approaches. Moreover, we will be able to make accurate predictions for experiments.