In this paper, we report high-pressure Raman experiments (0 − 28 GPa) in two different systems, i.e., linear carbon chains encapsulated by multi-walled (C_n@MWCNTs) and double-walled (C_n@DWCNTs) carbon nanotubes. By running high-pressure cycles, it is observed basically two changes in the Raman spectra of chains that are the softening and disappearance of C_n modes. We attributed the irreversible redshift of the C_n band to the coalescence between adjacent chains. On the other hand, the disappearance of the C_n band at the onset of the CNT collapse pressure is assigned to the tube-chain cross-linking. This effect appears to be independent of the C_n length and the number of walls of the tubes, depending only on the innermost CNT diameter. We show that the pressure to coalesce longer chains is higher than 10 GPa. Density functional theory and molecular dynamics calculations were performed in order to support the interpretation of experimental data. The calculations show an irreversible pressure-induced softening of frequency of the confined linear carbon chain. Furthermore, molecular dynamics calculations showed that coalescence between the shorter chains occurs in a region of lower pressure than that of the longer chains, thus supporting the experimental observations. Our findings shed new light on the understanding of the C_n@CNT system stability and pave the way for using high-pressure to obtain ultra-long chains (at lower pressures) and ultra-hard composites (at higher pressures).

在本文中，我们报告了两种不同系统中的高压拉曼实验 (0 - 28 GPa)，即由多壁 (C _n @MWCNTs) 和双壁 (C _n @DWCNTs) 碳纳米管封装的线性碳链. 通过运行高压循环，基本上观察到链的拉曼光谱中的两个变化，即C _n模式的软化和消失。_{我们将 C n}带的不可逆红移归因于相邻链之间的聚结。另一方面，在CNT塌陷压力开始时C _n带的消失归因于管链交联。这种效应似乎与 C _n无关管的长度和壁数，仅取决于最内层的 CNT 直径。我们表明，合并较长链的压力高于 10 GPa。为了支持实验数据的解释，进行了密度泛函理论和分子动力学计算。计算显示受限线性碳链的频率发生不可逆的压力诱导软化。此外，分子动力学计算表明，较短链之间的聚结发生在压力低于较长链的区域，从而支持了实验观察。我们的发现为理解 C _{n提供了新的思路}@CNT 系统稳定性并为使用高压获得超长链（在较低压力下）和超硬复合材料（在较高压力下）铺平了道路。