Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA.
Phys Rev Lett. 2010 May 7;104(18):185702. doi: 10.1103/PhysRevLett.104.185702. Epub 2010 May 5.
We develop an all-electron quantum Monte Carlo (QMC) method for solids that does not rely on pseudopotentials, and use it to construct a primary ultra-high-pressure calibration based on the equation of state of cubic boron nitride. We compute the static contribution to the free energy with the QMC method and obtain the phonon contribution from density functional theory, yielding a high-accuracy calibration up to 900 GPa usable directly in experiment. We compute the anharmonic Raman frequency shift with QMC simulations as a function of pressure and temperature, allowing optical pressure calibration. In contrast to present experimental approaches, small systematic errors in the theoretical EOS do not increase with pressure, and no extrapolation is needed. This all-electron method is applicable to first-row solids, providing a new reference for ab initio calculations of solids and benchmarks for pseudopotential accuracy.
我们开发了一种不依赖赝势的全电子量子蒙特卡罗(QMC)方法，并将其用于构建基于立方氮化硼状态方程的主要超高压校准。我们使用 QMC 方法计算了自由能的静态贡献，并从密度泛函理论获得了声子贡献，从而得到了高达 900 GPa 的高精度校准，可直接在实验中使用。我们通过 QMC 模拟计算了压力和温度下的非谐拉曼频率位移，从而实现了光学压力校准。与目前的实验方法相比，理论 EOS 中的小系统误差不会随压力增加，也不需要外推。这种全电子方法适用于第一行固体，为固体的从头算计算提供了新的参考，并为赝势精度提供了基准。
