Investigação da assinatura Raman de monocamadas de γ−grafinos: uma abordagem por primeiros-princípios

Abstract

Carbon allotropes are distinguished by their structure and hybridization. Some examples are the diamond, in which atoms are hybridized to sp3

, graphite, carbon nanotubes, graphene and ful- lerene, in which carbon is hybridized to sp2

, and graphynes , in which carbon has both sp and sp2 hybridizations. In graphynes, studied in this work, the C −C bonds that connect benzene rings in the graphene are replaced by acetylene units, generating single-atom hexagonal-pattern crystalline structures with larger diameter of the pores. These structural differences result in

a wide variety of mechanical, optical, chemical and electronic properties, reflecting in diffe- rent application perspectives. In 2010 and 2018 the graphines formed by chains of two and

four acetylenes, called graphdiyne and graphtetrayne, respectively, were synthesized. They

have semiconductor properties in the case of graphdiyne in its volumetric form. Their appli- cations are vast, from batteries to molecular filters. Raman spectroscopy is a cheap, fast, and

generally non-destructive technique for structure characterization through the study of nano- materials vibrations and widely used in carbon based materials. However, a systematic study

of the differences in vibrational spectroscopic responses for graphynes with different acetylene compositions is still required. In this work we use first principle calculations (DFT) to simulate the Raman spectrum of graphyne monolayers with one, two, three, four, five and six acetylene units. Our results can help in the identification of the type of synthesized graphyne and reveal details of the atomic vibration patterns and their symmetries, providing key strategies for the architecture of new applications of these materials.