3. Settings
KITE uses the classes kite.Configuration
and kite.Calculation
to define the calculation settings.
This is what a typical kite.Configuration
object (for a 2D lattice) looks like:
kite.Configuration
object.
Divisions¶
 The
divisions
is an integer number that defines the number of decomposition parts in each spatial direction. KITEx implements a domain decomposition technique to divide the lattice into various partitions that are computed in parallel. The domain decomposition is optimized at the design level and allows a substantial speed up of multithreaded calculations, it's usage is recommended.  To activate this feature, set a number of decomposition parts larger than one
nx * ny * nz > 1
.Warning
The product
nx * ny * nz
equals the number of threads used by KITEx and thus must not exceed the number of available cores in the computer.
Length¶

The
length
is an integer number of unit cells along the direction of lattice vectorslx, ly, lz = 256, 256, 256
. The lateral size of the decomposed parts are given bylx/nx
andly/ny
.Warning
The laterial sizes
lx/nx
,ly/ny
,lz/nz
must be integers. 
When using a 2D lattice, only
lx, ly, nx, ny
are needed.
Boundaries¶

KITE has 3 standard types of boundary conditions (BCs) implemented, namely: periodic, open, and twisted. Moreover, a "random BCs" option is available, whereby statistical averages over ensembles of random vectors (or disorder configurations) are done with the help of random twist angles drawn from a uniform distribution. This special option is particularly useful to simulate the infinitesize “bulk", since it efficiently eliminates finite size effects.
Info
It is possible to impose open BCs along one spatial direction to build ribbons in 2D and slabs in 3D.
The
boundaries
is a string, use'periodic'
for periodic BCs,'open'
for open BCs,'twisted'
for twisted BCs and'random'
for random BCs. In all cases, the system has the geometry of the unit cell, which is replicatedlx, ly, lz
times in the directions of the unit vectors. Different BCs can be used along thex, y
andz
axis. If twisted boundary conditions are used, the twistangles
must be included in radians.Twisted BC¶
For twisted BCs, the twist phase angles need to be specified by the user. This is done by means of an extra argument
' angles=[phi_1,..,phi_DIM]'
where' phi_i \in [0, 2*M_PI]'
. The syntax is simple:Random BC¶
Random BCs are defined using
mode = 'random'
. No extra arguments are required, but this option implicitely assumes that many random vectors (and/or disorder configurations) will be used. For a single system realization (Sec. calculation for calculation settings), this option is equivalent to a mere twistedBC simulation with randomly chosen twistangles alongx, y
andz
axis.Warning
The usage of
True
orFalse
for the boundaries is deprecated.
Complex¶
 The
is_complex
is a boolean value. For optimisation purposes, KITEx only considers and stores complex data with the settingis_complex=True
.False
should be used for real symmetric Hamiltonians.
Precision¶
 The
precision
is an integer identifier for the used data type. KITEx allows users to define the precision of the calculation. Use0
for float,1
for double, and2
for long double.
Spectrum Range¶

The optional
spectrum_range
is an array of reals. By default, KITEx executes an automated rescaling of the Hamiltonian, see the Documentation. Advanced users should avoid the automated rescaling and override this feature usingspectrum_range=[Emin,Emax]
, whereEmin, Emax
are the minimum, maximum eigenvalues of the TB matrix. Lower/upper bounds on smallest/largest energy eigenvalues should be used if exact eigenvalues are unknown (often the case in systems with disorder); see Sec. Disorder for more information.To manually set the
spectrum_range
, it is necessary to add an extra parameter to thekite.Configuration
class: