Electronic properties of 2D and 1D systems

Prev:LabQSM#Module 3: Low dimensional structures (6h)

Input set up for a low dimensional system:

Now we want to deal with systems of reduced dimensionality, e.g. periodic in one or two dimension but isolated in the other directions. This is accomplished by:

• Isolating the system in the non-periodic dimension as seen in the

K-points and Gamma sampling

• The Brillouin zone of a infinitely large cell subject to PBC becomes a single point, Gamma. Because of this, even when using a large but finite cell, K-point sampling should not be used. This should not be relevant in terms of results (if it is, spurious interactions are present), but would result in a waste of computational resources. The so-called Gamma sampling should then be sued.
• Moreover, in view of the Gamma sampling, wave functions can be taken to be real, leading to more memory and computational time savings.
• In Quantum ESPRESSO one needs to set the following:

  K_POINTS automatic
  1 1 1   0 0 0         # for Gamma sampling using complex wavefunctions
                        # deprecated, unless for testing or debugging