Structural modifications of graphyne layers consisting of carbon atoms in the sp- and sp 2-hybridized states

Abstract

A model scheme is proposed for obtaining layered compounds consisting of carbon atoms in the sp and sp 2 hybridized states. This model is used to find the possibility of existing the following seven basic structural modifications of graphyne: α , β1 , β2 , β3 , γ1 , γ2 , and γ3 graphyne. Polymorphic modifica tions β3 graphyne and γ3 graphyne are described. The basic structural modifications of graphyne contain diatomic polyyne chains and consist only of carbon atoms in two different crystallographically equivalent states. Other nonbasic structural modifications of graphyne can be formed via the elongation of the carbyne chains that connect three coordinated carbon atoms and via the formation of graphyne layers with a mixed structure consisting of basic layer fragments, such as α-β graphyne, α-γ graphyne, and β-γ graphyne. The semiempirical quantum mechanical MNDO, AM1, and PM3 methods and ab initio STO6 31G basis calcu lations are used to find geometrically optimized structures of the basic graphyne layers, their structural parameters, and energies of their sublimation. The energy of sublimation is found to be maximal for γ2 gra phyne, which should be the most stable structural modification of graphyne.

New nanostructures of carbon: Quasi-fullerenes Cn-q (n = 20, 42, 48, 60)

“…All calculations were performed using the 6-31G(d) basis set [48,49]. This level of theory B3LYP/6-31G (d) has been widely used for the study of allotropic forms of carbon, successfully predicting the experimentally observed geometries [18][19][20][21][22][23][24][25][26]35]. Frequency calculations were carried out at the same level of theory in order to confirm that the optimized structures correspond to a local minimum.…”

“…Nevertheless, the IPR is not commonly satisfied with the small fullerenes, due to the possibility to form a great variety of isomers, since the small differences in formation energies of each isomer make difficult to identify [11][12][13][14][15][16]. Therefore, theoretical studies of all possible isomers that can be form with small fullerenes have been performed using molecular dynamics [17,18], semi-empirical [14,18,24] and DFT methods [12,13,15,16,[20][21][22][23][24][25][26][27].…”

“…On the other hand, the synthesis of small carbon structures opens a new field of research in the study of new allotropic forms of carbon that have not been reported [17][18][19][20][21][22][23][24]32]. In general polyhedral closed cages made up entirely of n three-coordinate carbon atoms shall be known as quasi-fullerenes [7].…”

“…One novel method employed to find other forms of allotropic carbon is through molecular dynamics methods, where implemented algorithms allow the search of new quasi-fullerenes with regular and semi-regular polyhedral shapes [24]. Molecular Dynamics represents another choice to find other forms of allotropic carbon [17,18,24], where structures of regular shapes and semi-regular polyhedral have been found. In recent years, Belenkova and Shahova [32] reported some structures of carbon using molecular mechanics method (MM+).…”

Structure and electronic properties of graphyne layers modeled on layers of graphene L3–12

“…Однако впервые экспериментально синтезировать одну из структурных разновидностей графина -графдиин (graphdiyne) удалось только в 2010 [8]. В ряде недавних теоретических исследований была предложена модельная схема построения всех возможных структурных разновидностей графина в результатате трансформации структуры исходных графеновых слоев [9,10]. Для ряда графиновых слоев построенных при помощи этой модельной схемы на основе слоев графена L 6 и L 4-12 был выполнен расчет оптимальной структуры и свойств [9 -12].…”