Mello S L A, Pereira R C, Codeço C F S, Martinez R, da Silveira E F, Sant'Anna M M
Departamento de Física, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil.
Departmento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro, RJ, Brazil.
J Phys Chem A. 2024 Aug 29;128(34):7073-7083. doi: 10.1021/acs.jpca.4c02709. Epub 2024 Aug 16.
A new method to investigate disorder in ice films is proposed and applied to acetylene ice. It is based on a quantitative analysis of the infrared spectrum data, which includes: the Brendel-Bormann model for the material's dielectric function; molecular vibration modes calculated by density functional theory (DFT); a monomer-dimer model for amorphous ice; and a peak-shape analysis through Levenberg-Marquardt nonlinear regression. Acetylene ice films with different degrees of disorder were investigated with the proposed method. The results provide an estimate of the degree of disorder in the films and indicate the possibility of existence of a second amorphous phase of acetylene ice grown at temperatures of about 15 K and then annealed. This phase would be similar to the high-density amorphous phase observed for water ice. The infrared data in this work is compared with those from the literature for acetylene gas, acetylene film, and acetylene aerosol. A qualitative analysis reveals differences in the degree of disorder in each system and points to a crystallinity limit for acetylene ice film; that is, the crystalline acetylene film has a higher degree of intrinsic disorder than the crystalline acetylene aerosol.
提出了一种研究冰膜无序性的新方法，并将其应用于乙炔冰。该方法基于对红外光谱数据的定量分析，包括：材料介电函数的布伦德尔 - 博尔曼模型；通过密度泛函理论（DFT）计算的分子振动模式；非晶冰的单体 - 二聚体模型；以及通过列文伯格 - 马夸尔特非线性回归进行的峰形分析。用该方法研究了不同无序度的乙炔冰膜。结果给出了膜中无序度的估计，并表明在约15 K温度下生长然后退火的乙炔冰可能存在第二个非晶相。该相类似于在水冰中观察到的高密度非晶相。将这项工作中的红外数据与文献中关于乙炔气体、乙炔膜和乙炔气溶胶的数据进行了比较。定性分析揭示了每个系统中无序度的差异，并指出了乙炔冰膜的结晶度极限；即，结晶乙炔膜比结晶乙炔气溶胶具有更高的固有无序度。
