Modeling mechanical properties of carbon molecular clusters and carbon nanostructural materials
- PDF / 133,340 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 93 Downloads / 170 Views
I7.2.1
Modeling mechanical properties of carbon molecular clusters and carbon nanostructural materials
Vadim M.Levin, Julia S.Petronyuk, Inna V.Ponomareva Lab. of Acoustic Microscopy, Inst.of Biochemical Physics, Russian Academy of Sciences, 4 Kosygin St., Moscow, 119991, Russia
ABSTRACT The concept of 2D elasticity of a graphene sheet together with the idea of stiffness of a single sp3 bond have been applied to theoretical evaluating elastic properties of diverse carbon states. 2D elastic moduli have been extracted from data on elastic moduli of crystalline graphite. Stiffness of the sp3 bond has been estimated from data on the elastic modulus of diamond. Efficiency of Van-der-Waals interaction has been taken from the elastic modulus C33 of crystalline graphite. Characteristics of single fullerene deformability have been computed by the molecular dynamics method. Theoretical estimations have been performed for single molecular clusters, pristine fullerite, HPHT phases of polymerized C60, etc. The estimations are in good agreement with experimental data on elastic properties and nanoscale structure of carbon states. The approach is effective for establishing interrelation between nanostructure and elastic properties, for prediction and classification of nanostructure in novel carbon materials. Three types of hybridized covalent bonds between of carbon atoms (sp3, sp2 and sp) give rise a variety of macromolecular clusters and carbon nanostructural solids, which are essentially distinguished in their mechanical properties. Diversity of mechanical characteristics stems from the variability in nanostuctural organization and from combination of different types of covalent bonds (sp2 and sp3) with Van-der-Waals interaction between molecular clusters. The purpose of the paper is to explain the elastic property diversity in the frame of simple mechanical models of different nanoscale structures using, in the main, data on elastic properties of well-known carbon states – graphite and diamond. Analysis of these models makes it possible to follow variations in elastic characteristic of carbon states in transition from one form of nanostructural organization to another. The most of carbon states are formed by 2D structural units – plane or curved graphene sheets or closed molecular clusters (fullerenes, nanofilaments, etc) originated from these sheets. Vander-Waals forces or covalent sp3 bonds provide 3D linkage between the 2D graphite-like nanostructural elements. Diversity of carbon states actually results from two specific peculiarities of hybridized C-C bonds. The first is high lability – interatomic distances and valent angles are liable to vary over relatively wide range. Stressed sp2 bonds cause bending graphite sheets – curved atomic sheets are inherent in many carbon states: carbon fibers, fullerenes, nanotubes and so on. The other feature of carbon is concurrent participation of different types of C-C bonds in formation of carbon states. Normally the spatial structure of carbon materials is formed by Vander-Waals i
Data Loading...
