Applications
The NANOQUANT project has objectives referring to both basic science and
applications. At the low end, the objective is to develop a conceptually and
mathematically consistent rigorous electronic-structure toolbox, applicable
at the nanoscale and intended for accurate calculations (the prediction of
properties), for understanding (the interpretation of properties), and for
testing simpler models with wider ranges of applicability. At the high end,
our goal is for the network to act as an active modelling unit, providing
theoretical support to experimental activities such as synthesis, materials
characterization, and the "design of devices". Quantum modelling can
contribute at all stages of such a project: at its inception, to predict
the sought-after property and to screen classes of compounds or structures
for subsequent experimental study and synthesis; at its conclusion, to build
models and to establish relationships between properties of interest and
structure (geometric and electronic) or between properties and functions
of compounds.
The research will be conducted within six interconnected areas:
1. Nanoscale quantum modelling.
An essential objective of the network is to transfer the scale of quantum
modelling from the atomic domain into the nano domain. Indeed, without its
fulfillment, we cannot hope to reach the other objectives of understanding
nanomaterials from a quantum perspective and of modelling materials of
technological interest. A primary target of the network is therefore to
consolidate the linear-scaling techniques, i.e., techniques with a cost
proportional to the system size.
2. Large-scale developments of high-level correlation methods.
Due to its computational simplicity, the main thrust of the development of
quantum methods towards the nanoscale regime takes place within the realm
of density functional theory (DFT). Nevertheless, it is essential that a
similar development is also undertaken for the hierarchical ab initio
methods. These methods are not only important in themselves, in that they
enable rigorous calculations of molecular properties to chemical accuracy,
they are also important in that they provide capabilities for benchmarking
and tests of DFT. In ab initio theory, work with coupled-cluster theory,
the use of decomposition, Laplace transforms, and resolution-of-identity
(density-fitting) techniques will be conducted.
3. Multi-configurational relativistic DFT.
Apart from extending the scale and scope of the applicability range of
current electronic-structure techniques into the nano domain, it remains
important to study and develop the basic aspects of electronic-structure
theory. In particular, we shall here focus on the role of spin and spin
states in open-shell
systems, and on four-component relativistic electronic-structure theory.
4. Modelling of characterizing techniques.
We will focus on the modelling of various magnetic resonance processes ---
namely, nuclear magnetic resonance (NMR), electron paramagnetic
resonance (EPR), and optically detected magnetic resonance (ODMR). We
shall likewise pursue modelling of spectroscopic process in other regions
of the electromagnetic spectrum: vibrational Raman optical activity (VROA)
in the infrared region, natural and magnetically induced circular
dichroism in the optical region, and Raman scattering in the X-ray region.
5. Molecular and nano-electronics.
The network will focus on the development of a nonequilibrium Green's
function theory to describe the potential distribution and current-voltage
characterization of molecular devices. A goal is to predict the optimal
size and shape for metal contacts and molecular bridges of devices such
switches and transistors. The conductivity of nanotubes and biological
molecules will also be investigated.
6. Molecular and nano-photonics.
In the emergence of modern information society, the technology of
photonics plays a pivotal role. To fully understand the functionality of
various photonics devices such as conductors, wave guides, switches and
displays, it is essential to master and simulate the basic photon--matter
interaction. An task of the proposed NANOQUANT network is to consolidate
and extend the functionality of the existing fourth-order toolbox for
electromagnetic properties to the nanoscale regime, involving the
adaptation of density-matrix based response theory.
Theoretical Chemistry,
NANOQUANT
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