实验和计算研究由高能构象组成的结晶甲酸。

Experimental and computational study of crystalline formic acid composed of the higher-energy conformer.

机构信息

Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014, Finland.

出版信息

J Chem Phys. 2011 Feb 7;134(5):054506. doi: 10.1063/1.3533955.

Abstract

Crystalline formic acid (FA) is studied experimentally and by first-principles simulations in order to identify a bulk solid structure composed of the higher-energy (cis) conformer. In the experiments, deuterated FA (HCOOD) was deposited in a Ne matrix and transformed to the cis conformer by vibrational excitation of the ground state (trans) form. Evaporation of the Ne host above 13 K prepared FA in a bulk solid state mainly composed of cis-FA. Infrared absorption spectroscopy at 4.3 K shows that the obtained solid differs from that composed of trans-FA molecules and that the state persists up to the annealing temperature of at least 110 K. The first-principles simulations reveal various energetically stable periodic chain structures containing cis-FA conformers. These chain structures contain either purely cis or both cis and trans forms. The vibrational frequencies of the calculated structures were compared to the experiment and a tentative assignment is given for a novel solid composed of cis-FA.

摘要

为了确定由高能（顺式）构象组成的块状固体结构，我们对结晶甲酸（FA）进行了实验和第一性原理模拟研究。在实验中，氘代 FA（HCOOD）沉积在 Ne 基质中，并通过振动激发基态（反式）形式转化为顺式构象。在 13 K 以上蒸发 Ne 主体，将 FA 制备成主要由顺式-FA 组成的块状固体。在 4.3 K 下的红外吸收光谱表明，所得到的固体与由反式-FA 分子组成的固体不同，并且该状态至少持续到 110 K 的退火温度。第一性原理模拟揭示了含有顺式-FA 构象的各种能量稳定的周期性链结构。这些链结构包含纯顺式或顺式和反式两种形式。计算结构的振动频率与实验进行了比较，并对由顺式-FA 组成的新型固体进行了初步归属。