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www.crystal.unito.it.
Introduction
The CRYSTAL program was jointly developed by the
Theoretical Chemistry Group
at the University of Torino and the
Computational Materials Science group in STFC.
CRYSTAL is an all electron, first principles simulation code implementing both Hartree Fock and density functional approaches in periodic systems. The wave functions are expanded in atom-centred Gaussian type orbitals (GTOs) providing a highly efficient and numerically precise solution with no shape approximation to the density or potential. Powerful screening techniques are used to exploit real space locality. The code may be used to perform consistent studies of the physical, electronic and magnetic structure of molecules, polymers, surfaces and crystalline solids.
Resources for CRYSTAL Users
The current release of CRYSTAL is CRYSTAL09 which is available from the CRYSTAL home page which also provides documentation and a number of resources for CRYSTAL users. There are very useful tutorials to learn how to use CRYSTAL that range for beginners to advanced and these are recommended for beginners use. Tutorials
New Functionality
A Technical Report on the implementation of the climbing-image nudged elastic band
method within CRYSTAL is available here
For more information about CRYSTAL please contact
crystal@dl.ac.uk or
crystal@unito.it.
The DLVisualize Graphical User Interface
DL Visualize (DLV v3.0)
provides an interface to CRYSTAL and a number of other materials simulation
programmes. DLV supports geometry editing, job submission and the display
of structures and properties.
Projects using CRYSTAL.
The computational material sciences group at STFC use CRYSTAL as essential software in order to carry out their research. Some examples of projects done using CRYSTAL are:
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Magnetic coupling in V(TCNE)2
In this work, a model of V(TCNE)2 which satisfies a set of constraints based upon experimental evidence, is proposed. These constraints include (i) the observed stoichiometry, (ii) the suggested octahedral coordination for the metal ion, (iii) the presence of uncoordinated cyano groups, and (iv) the dimensionality of the material forming a periodic crystalline network of V atoms and TCNE molecules. Calculations of the structural, electronic, and magnetic properties of this model were performed using density functional theory as implemented in the CRYSTAL09 package.
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Catalysis of the CCl2F2 - Dis mutation Reaction on AlF3.
HFCs are synthesised via halogen exchange reactions of
CFCs and HF. Recently, there has been much interest in
the use of aluminium fluoride (AlF3) as such a catalyst [1].
High surface area (HS) AlF3 has been shown to act as a
very efficient catalyst for these reactions. In some cases
it is even more effective than the widely used Swartz
catalyst based on antimony pentafluoride.
We used state of the art hybrid density functional theory
to investigate the interaction of CCl2F2 with and to
study the energetics of the proposed reaction pathway.
The CRYSTAL program was used to
perform these calculations. Reaction pathways for the
dis mutation reaction were obtained using the nudged
elastic band (NEB) algorithm, of which has recently been
implemented in the CRYSTAL program. This algorithm
requires the structures of the initial and final states of the
transition pathway and an initial guess of the pathway.
The reaction pathway for the catalysis of 2CCl 2F 2 + CCl 3 on the surface of β-AlF 3
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Spin-qubits in Carbon Peapods.
Spin chains have the potential to provide the controlled
interactions needed for quantum computing. Carbon is a
candidate host for spin qubits because in 12C materials the
small spin-orbit coupling and absence of hyperfine coupling
ensures long spin coherence times. Carbon peapods, that is,
single-walled carbon nanotubes (SWNT) containing
fullerenes, have been proposed as particularly suitable spin
chain systems. The fabrication of nanoscale electronic
devices, such as field effect transistors, with carbon
peapods containing various endohedral fullerenes is well
established. When spin active metallic atoms such as Sc are
incarcerated in a carbon cage, the system develops
hybridized orbitals resulting in an unpaired electron
delocalized across the fullerene cage potentially a near
ideal qubit.
The CRYSTAL code was used to perform calculations based
on density functional theory (DFT).We find well-defined
spin-1/2 qubits on the fullerenes, with strong evidence for
a nearest-neighbour Heisenberg exchange interaction. In
order to describe the influence on the spin-qubits localized
on the fullerenes of propagating electrons or holes in the
nanotube, it is necessary to go beyond DFT to a model
which is capable of describing the low-energy charge-spin
excitations of the system. We conjecture a generic
Hubbard-Anderson model; which captures the Heisenberg
exchange between spins along the fullerene chain and the
Kondo exchange interaction between localized spins on the
fullerenes and spins of propagating electrons or holes in
the nanotube.
CRYSTAL in Parallel
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Massively Parallel CRYSTAL Calculations
The code implements Hartree Fock and density functional theory using a local Gaussian basis set providing for the accurate calculation of energy and forces for structural optimisation and a wide variety of material properties.
The massively parallel implementation of CRYSTAL allows systems with ~1000 atoms per unit cell to be studied routinely on parallel computers. The two key computational steps are the evaluation of the Hamiltonian through the calculation of matrix element integrals and the solution of the Kohn Sham equations through diagonalisation of the Hamiltonian.
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