Transcript Graphene crystal

Graphene
Part of
MATERIALS SCIENCE
& A Learner’s Guide
ENGINEERING
AN INTRODUCTORY E-BOOK
Anandh Subramaniam & Kantesh Balani
Materials Science and Engineering (MSE)
Indian Institute of Technology, Kanpur- 208016
Email: [email protected], URL: home.iitk.ac.in/~anandh
http://home.iitk.ac.in/~anandh/E-book.htm
Graphene
 Carbon is perhaps the most fascinating element in nature
 The principal forms of carbon are:
 Graphite
 Diamond
 Fullerene, nanotubes and related structures
 A single sheet of graphite is called graphene
 It is sp2 hybridized  covalently bonded
 The bonding between the graphene sheets in graphite is of van der Walls type
 In this set of slides we consider crystallographic concepts related to graphene
 It is a hexagonal array of Carbon atoms, which is NOT a lattice
Part of the hexagonal array of C atoms which forms
the Graphene structure
Not all carbon positions
form a lattice
As atoms A & B do not
have identical surrounding
both cannot be lattice
points
Structure of single graphene sheet
Crystal = Lattice + Motif
Grey atoms sit on the
lattice positions
Motif = 1 grey + 1 green
(in positions as shown)
 Either the green or the grey carbon atoms can
be considered to be located at lattice points
(but not both)
 In plane motif consists of two C atoms
 The unit cell is as marked