This article reviews the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudopotential method. Several specialized topics are treated, including the implementation for metals, the calculation of the response to macroscopic electric fields and their relevance to long-wavelength vibrations in polar materials, the response to strain deformations, and higher-order responses. The success of this methodology is demonstrated with a number of applications existing in the literature.

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Phonons and related crystal properties from density-functional perturbation theory

Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene.

/pdf/raman-spectroscopy-as-a-versatile-tool-for-studying-the-54mhwmcfzi.pdf

Raman spectroscopy as a versatile tool for studying the properties of graphene

Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures.

https://science.sciencemag.org/content/sci/258/5087/1474.full.pdf

Photoinduced electron transfer from a conducting polymer to buckminsterfullerene.

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Raman spectroscopy of carbon nanotubes

Functionalization of carbon nanotubes

Resonance Raman and infrared spectroscopy of carbon nanotubes

The mystery of the 1140 cm−1 Raman line in nanocrystalline diamond films

Electronic Properties of Conjugated Polymers III

The radial breathing mode is a promising candidate for the analysis of conformational and electronic properties of carbon nanotubes. The paper presents calculations based on the local density approximation to determine the radial breathing mode (RBM) frequency of various zigzag and armchair tubes with radii between 3.5 and 8.1 \AA{}. The frequencies are derived from both frozen phonon calculations for nanotubes and from the elastic constants of the flat graphene sheet. The RBM frequency of the (10,10) armchair tube is found to be $175{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and $174{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ for the two techniques, respectively. These values are in very good agreement with one of the strongest components in the structured Raman band of the radial breathing modes observed at $177{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}.$ Since the RBM frequency turns out to scale with $1/R$ the calculations also allow one to evaluate the frequency of this mode for tubes with arbitrary chirality.

Hans Kuzmany

Papers

Functionalization of carbon nanotubes

Resonance Raman and infrared spectroscopy of carbon nanotubes

The mystery of the 1140 cm−1 Raman line in nanocrystalline diamond films

Electronic Properties of Conjugated Polymers III

First-principles calculations of the radial breathing mode of single-wall carbon nanotubes