Specific heat capacity is one of the most fundamental thermodynamic properties of materials. In this work, we measured the specific heat capacity of PbSe nanocrystals with diameters ranging from 5 to 23 nm, and its value increases significantly from 0.2 to 0.6 J g^–1 °C^–1. We propose a mass assignment model to describe the specific heat capacity of nanocrystals, which divides it into four parts: electron, inner, surface, and ligand. By eliminating the contribution of ligand and electron specific heat capacity, the specific heat capacity of the inorganic core is linearly proportional to its surface-to-volume ratio, showing the size dependence. Based on this linear relationship, surface specific heat capacity accounts for 40–60% of the specific heat capacity of nanocrystals with size decreasing. It can be attributed to the uncoordinated surface atoms, which is evidenced by the appearance of extra surface phonons in Raman spectra and ab initio molecular dynamics (AIMD) simulations.

中文翻译：

---

PbSe 纳米晶体的尺寸依赖性比热容

比热容是材料最基本的热力学性质之一。在这项工作中，我们测量了直径范围为5至23 nm的PbSe纳米晶的比热容，其值从0.2显着增加至0.6 J g ^–1 °C ^–1。我们提出了一个质量分配模型来描述纳米晶体的比热容，该模型将其分为四个部分：电子、内部、表面和配体。通过消除配体和电子比热容的贡献，无机核的比热容与其表面积与体积比成线性正比，显示出尺寸依赖性。根据这种线性关系，随着尺寸的减小，表面比热容占纳米晶比热容的40-60%。这可以归因于不协调的表面原子，拉曼光谱和从头算分子动力学 (AIMD) 模拟中额外表面声子的出现证明了这一点。