# DielectricCylinder#

class maicos.modules.dielectriccylinder.DielectricCylinder(atomgroup, bin_width=0.1, temperature=300, single=False, output_prefix='eps_cyl', refgroup=None, concfreq=0, dim=2, rmin=0, rmax=None, zmin=None, zmax=None, vcutwidth=0.1, unwrap=True)[source]#

Bases: CylinderBase

Calculate cylindrical dielectric profiles.

Components are calculated along the axial ($$z$$) and radial ($$r$$) direction either with respect to the center of the simulation box or the center of mass of the refgroup if provided. The axial direction is selected using the dim parameter.

For usage please refer to How-to: Dielectric constant and for details on the theory see Dielectric constant measurement.

Also, please read and cite [1].

Parameters:
• atomgroup (AtomGroup) – A AtomGroup for which the calculations are performed.

• refgroup (AtomGroup) –

Reference AtomGroup used for the calculation.

If refgroup is provided, the calculation is performed relative to the center of mass of the AtomGroup.

If refgroup is None the calculations are performed to the center of the (changing) box.

• unwrap (bool) –

When unwrap = True, molecules that are broken due to the periodic boundary conditions are made whole.

If the input contains molecules that are already whole, speed up the calculation by disabling unwrap. To do so, use the flag -no-unwrap when using MAICoS from the command line, or use unwrap = False when using MAICoS from the Python interpreter.

Note: Molecules containing virtual sites (e.g. TIP4P water models) are not currently supported in MDAnalysis. In this case, you need to provide unwrapped trajectory files directly, and disable unwrap. Trajectories can be unwrapped, for example, using the trjconv command of GROMACS.

• concfreq (int) – When concfreq (for conclude frequency) is larger than 0, the conclude function is called and the output files are written every concfreq frames

• dim (int) – Dimension for binning (x=0, y=1, z=2).

• zmin (float) –

Minimal coordinate for evaluation (in Å) with respect to the center of mass of the refgroup.

If zmin=None, all coordinates down to the lower cell boundary are taken into account.

• zmax (float) –

Maximal coordinate for evaluation (in Å) with respect to the center of mass of the refgroup.

If zmax = None, all coordinates up to the upper cell boundary are taken into account.

• jitter (float) –

If jitter is not None, random numbers of the order of jitter (Å) are added to the atom positions.

The appilication of a jitter is rationalized in possible aliasing effects when histogramming data, i.e., for spatial profiles. These aliasing effects can be stabilized with the application of a numerical jitter. The jitter value should be about the precision of the trajectory and will not alter the results of the histogram.

You can estimate the precision of the positions in your trajectory with maicos.lib.util.trajectory_precision(). Note that if the precision is not the same for all frames, the smallest precision should be used.

• bin_width (float) – Width of the bins (in Å).

• rmin (float) – Minimal radial coordinate relative to the center of mass of the refgroup for evaluation (in Å).

• rmax (float) –

Maximal radial coordinate relative to the center of mass of the refgroup for evaluation (in Å).

If rmax=None, the box extension is taken.

• temperature (float) – temperature (K)

• single (bool) – For a single chain of molecules the average of M is zero. This flag sets <M> = 0.

results.bin_pos#

Bin positions (in Å) ranging from rmin to rmax.

Type:

numpy.ndarray

results.eps_z#

Reduced axial dielectric profile $$(\varepsilon_z - 1)$$ of the selected atomgroup

Type:

numpy.ndarray

results.deps_z#

Estimated uncertainty of axial dielectric profile

Type:

numpy.ndarray

results.eps_r#

Reduced inverse radial dielectric profile $$(\varepsilon^{-1}_r - 1)$$

Type:

numpy.ndarray

results.deps_r#

Estimated uncertainty of inverse radial dielectric profile

Type:

numpy.ndarray

References

save()[source]#

Save result.