Paul Plachinda

Electronic properties of metal-arene functionalized graphene

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M = Ti, V, Cr, Mn, Fe) molecules leads to an opening in the bandgap of graphene (up to 0.81 eV for the Cr derivative), and as a result, transforms it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

Modulated structure of Lu4AlCu2B9O23 from low- temperature single-crystal X-ray data

A second-order phase transition with both displacive and disorder mechanisms was discovered in Lu4AlCu2B9O23 using single-crystal X-ray diffraction techniques by cooling down the sample to 110 K. Low-temperature structure modulations are mainly associated with Cu atoms surrounded by O atoms. The fivefold asymmetric environment leads to a special copper position splitting into a pair of general ones so that four O atoms coordinate each of them. Each copper site is 50% occupied at room temperature, but at lower temperature statistical disorder gives occupation and displacive modulations with a wavevector of q = 0.132c*. Tetragonal P\bar 42(1)m symmetry of the non-modulated phase transforms into an orthorhombic (3+1)-dimensional symmetry, P21212(00γ)00s, whereas the \bar 4 axis becomes the twinning axis.

Thermal Conductivity of Graphene Nanoribbons: Effect of the Edges and Ribbon Width

We have calculated thermal conductance of graphene nanoribbons (GNRs) and their dependence on the type of ribbon edge termination (zigzag or armchair) and the width of the ribbon, which ranges from 50 A to 50 μm. Our model incorporates the effect of edge roughness and includes edge roughness correlation functions for both types of termination. The dependence of thermal conductance on the width of the ribbons and relative contribution of different scattering mechanisms are also analyzed by means of the Green’s function approach to the edge scattering. High temperature thermal conductance of the nanoribbons was found to be 0.15 nW/K and 0.18 nW/K (corresponding to thermal conductivity, 4641 and 5266 W/mK, respectively, for 10 μm long GNRs) which is in a good agreement with the experimental results.

Modification of graphene band structure by haptic functionalization

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and as a result, transforms it from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.