Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.
Department of Chemistry, Columbia University, New York, New York 10027, USA.
Phys Rev Lett. 2019 Jan 18;122(2):026101. doi: 10.1103/PhysRevLett.122.026101.
Material properties depend sensitively on the atomic arrangements and atomic bonding, but these are notoriously difficult to measure in nanosized atomic clusters due to the small size of the objects and the challenge of obtaining bulk samples of identical clusters. Here, we have combined the recent ability to make gram quantities of identical semiconductor quantum-dot nanoparticles with the ability to measure lattice dynamics on small sample quantities of hydrogenated materials using high energy resolution inelastic x-ray scattering, to measure the size dependence of the phonon density of states in CdSe quantum dots. The fact that we have atomically precise structural models for these nanoparticles allows the calculation of the phonon density of states using density functional theory, providing both experimental and theoretical confirmations of the important role that the inertia of the surface capping species plays on determining the lattice dynamics.
材料性能对原子排列和原子键合非常敏感，但由于纳米级原子团簇的体积小，以及获得相同团簇的大量块状样品具有挑战性，这些原子排列和原子键合很难进行测量。在这里，我们将近期能够制备出大量相同半导体量子点纳米粒子的能力与使用高能量分辨率非弹性 X 射线散射在少量氢化材料上测量晶格动力学的能力相结合，来测量 CdSe 量子点中声子态密度随尺寸的变化。对于这些纳米粒子，我们有原子精度的结构模型，这使得我们可以使用密度泛函理论来计算声子态密度，从而为表面覆盖物的惯性在确定晶格动力学方面的重要作用提供了实验和理论上的证实。
