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G P Srivastava  Research interests
My research has concentrated on theoretical and computational studies
of the physics of phonons and electrons in crystalline solids,
surfaces and nanostructures. I have collaborated with various
physicists, both experimentalists and theorists, of international
reputation. This has led to over 390 publications, including two
postgraduate books entitled The Physics of
Phonons and Theoretical Modelling of
Semiconductor Surfaces.
Current areas of research
Phonon Engineering of Nanocomposite Thermoelectric Materials
Thermoelectricity (TE) is the process of generating either electricity
from heat engines or heating devices from electricity. Examples of
modern TE applications include portable refrigerators, beverage
coolers, electronic component coolers, infrared sensing, etc. Possible
future applications of TE devices include efficient conversion of
waste heat (e.g. from waste and during powering of vehicles, etc) into
usable energy, in improving the efficiency of photovoltaic cells, etc.
It is being realised that material choice with reduced dimensionality
is a prudent strategy for increasing the TE figureofmerit (ZT)
relative to bulk values. It is further believed that significant
enhancement in ZT can be achieved by producing huge reduction in the
lattice (phonon) thermal conductivity by fabricating 'nanocomposites'
(in the form of superlattices, nanowired embedded matrices of larger
dimensions, or nanodots embedded in matrices of larger dimensions).
We are making a systematic theoretical investigations of this aspect
by considering Sibased, Bi2Te3based and PbTebased nanocomposites.
Nanophononic Solids
Our aim is to establish trends and criteria for the development of
polarisation gaps as well as total band gaps in the phonon spectrum of
1D, 2D and 3D nanophononic semiconductor systems. These studies are
made by employing a combination of the adiabatic bond charge model and
the DFTbased firstprinciples pseudopotential method. We are
developing a theory of phonondefect and phononphonon interactions,
and of phonon conductivity in such systems. These investigations are
based on a combination of anharmonic elastic continuum theory,
timedependent perturbation theory, and a model relaxation time
approach for the solution of the phonon Boltzmann equation. Project
support: Leverhulme Trust.
Nanomaterials
We are working on studies of the structural (equilibrium atomic
positions), electronic states, phonon modes, phonon interactions, and
thermal conductivity of semiconductor nanomaterials, such as wires and
superlattices. Theoretical methods employed include the adiabatic
bond charge model, the DFTbased firstprinciples pseudopotential
method, a model relaxation time theory for thermal conductivity.
Graphene Systems
We investigate equilibrium atomic geometry, stable structural shapes,
electronic states, magnetic properties, phonon modes, and phonon
lifetimes in graphene systes including monolayer graphene, bilayer
graphene, multilayer graphene, graphite, and graphene nanoribbons.
Theoretical methods include a combination of the DFTbased
firstprinciples pseudopotential method, and an anharmonic elastic
continuum theory. Collaborator: Dr. R. H. Miwa (University of
Uberlandia, Brazil).
Solid Surfaces
We make firstprinciples studies of adsorption and reactions on solids
surfaces. (a) Atomic geometry, electronic states and phonon
dispersion relations of clean semiconductor and metal surfaces.
Collaborator: Professor H. M. Tutuncu (Sakarya University, Turkey).
(b) Adsorption of atoms on IIIV(001) surfaces. (c) Molecular
adsorption on Si(111). Collaborators: Professor A. B. McLean
(Queen's University, Canada) and Dr. R. H. Miwa (University of
Uberlandia, Brazil). (d) Molecular adsorption on Si(100).
Collaborator: Dr. M. Shimomura (Shizuoka University, Japan). (e)
Dilute magnetic systems  atomic adsorption on IIIV(110).
Collaborator: Dr. M. Migliorato (Manchester University).
Bulk crystals
Firstprinciples studies of groundstate properties, electronic
structure, lattice dynamics, electronphonon interactions in the
context of BCS theory of superconductivity. Collaborator: Professor
H. M. Tutuncu (University of Sakarya, Turkey).
Previous Research
1970s:
Anharmonic phonon interactions; Theory of lattice thermal
conductivity; Empirical pseudopotential method for electronic band
structure of semiconductors; Pseudopotential theory of deep impurities
in semiconductors.
1980s:
Firstprinciples studies of atomic geometry, reconstrction and
electronic structure of solids and semiconductor surfaces using the
planewave pseudopotential method and the Density Function theory;
Development of the pseudopotentialDFT and a simple GW theory and
computer codes; Formulation and use of Broyden's Jacobian update
method for accelerated selfconsistent calculations.
1990s:
Development of theory and computer codes for lattice dynamical studies
(i.e. phonon dispersion relations and phonon eigen displacements) of
semiconductors and their surfaces using the adiabatic bond charge
model and the firstprinciples pseudopotential method.
2000s:
Firstprinciples studies of surface adsorption and reactions.
Firstprinciples studies of lattice dynamics using the pseudopotential
method and the density functional scheme, to carry out full lattice
dynamics of bulk, surfaces, and nanostructures. Application of our
previously developed theory of anharmonic interactions and lattice
thermal conductivity to nanostructures.
A brief description of my past research projects is available below.
