Atomic Orbitals

Name AOCombineJOrbitals
Section Atomic Orbitals
Type logical
Default no

By default, Octopus creates two sets of atomic orbitals for j-dependent pseudopotentials. When doing ACBN0 functional, this leads to a Hubbard U for j=l-1/2 and one for j=l+1/2, unless hubbard_j is specified in the species block. By setting this variable to yes, one can instead define a single set of atomic orbitals that contains both the j=l-1/2 and j=l+1/2 orbitals. This is only relevant for spinor calculations with j-dependent pseudopotentials.

Name AOLoewdin
Section Atomic Orbitals
Type logical
Default no

This option determines if the atomic orbital basis is orthogonalized or not. This is done for using the Loewdin orthogonalization scheme. The default is set to no for the moment as this option is not yet implemented for isolated systems, and seems to lead to important egg-box effect

Name AONormalize
Section Atomic Orbitals
Type logical
Default yes

If set to yes, Octopus will normalize the atomic orbitals individually. This variable is ignored is AOLoewdin is set to yes.

Name AOSubmesh
Section Atomic Orbitals
Type logical

If set to yes, Octopus will use submeshes to internally store the orbitals with their phase instead of storing them on the mesh. This is usually slower for small periodic systems, but becomes advantageous for large supercells. Submeshes are not compatible with Loewdin orthogonalization. For periodic systems, the default is set to no, whereas it is set to yes for isolated systems.

Name AOThreshold
Section Atomic Orbitals
Type float
Default 0.01

Determines the threshold used to compute the radius of the atomic orbitals for DFT+U and for Wannier90. This radius is computed by making sure that the absolute value of the radial part of the atomic orbital is below the specified threshold. This value should be converged to be sure that results do not depend on this value. However increasing this value increases the number of grid points covered by the orbitals and directly affect performances.

Name AOTruncation
Section Atomic Orbitals
Type flag
Default ao_full

This option determines how Octopus will truncate the orbitals used for DFT+U. Except for the full method, the other options are only there to get a quick idea.

Options:

• ao_full:
  The full size of the orbitals used. The radius is controled by variable AOThreshold.
  
• ao_box:
  The radius of the orbitals are restricted to the size of the simulation box. This reduces the number of points used to discretize the orbitals. This is mostly a debug option, and one should be aware that changing the size of the simulation box will affect the result of the calculation. It is recommended to use ao_nlradius instead.
  
• ao_nlradius:
  The radius of the orbitals are restricted to the radius of the non-local part of the pseudopotential of the corresponding atom.