类金刚石电子发射的扩散量子蒙特卡罗研究
Electron Emission from Diamondoids: A Diffusion Quantum Monte Carlo Study
摘要：
我们提出了密度泛函理论（DFT）和量子蒙特卡罗（QMC）计算旨在解决H-封端的C纳米粒子（金刚石）的光学性质的实验和理论争议。QMC的结果遵循收敛良好的平面波DFT计算的光学间隙的尺寸依赖性的趋势，但他们预测的差距是1-2 eV高。他们证实，量子限制效应在大于1 nm的类金刚石中消失，这些类金刚石的间隙低于大块金刚石的间隙。我们的QMC计算预测一个小的激子结合能和负电子亲和力（NEA）的金刚烷高达1 nm，从离域性质的最低未占分子轨道。NEA提出了金刚石作为低压电子发射体的一系列可能的应用。
英文摘要：
We present density-functional theory (DFT) and quantum Monte Carlo (QMC) calculations designed to resolve experimental and theoretical controversies over the optical properties of H-terminated C nanoparticles (diamondoids). The QMC results follow the trends of well-converged plane-wave DFT calculations for the size dependence of the optical gap, but they predict gaps that are 1-2 eV higher. They confirm that quantum confinement effects disappear in diamondoids larger than 1 nm, which have gaps below that of bulk diamond. Our QMC calculations predict a small exciton binding energy and a negative electron affinity (NEA) for diamondoids up to 1 nm, resulting from the delocalized nature of the lowest unoccupied molecular orbital. The NEA suggests a range of possible applications of diamondoids as low-voltage electron emitters.
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