Describing semicore states with local orbitals
If the treatment of a semicore state as a core electron leads to a ghost band the user typically resolves this issue by switching the treatment of these respective electrons to a valence electron treatment. This procedure involves several steps that have to be performed in a consistent way.
The starting point is the identification of the responsible semicore states. This is done by identifying those core electron states with the highest eigenenergies.
For each atom type the eigenenergies of the core electron states are provided in the
elements of the
out.xml file. The number of core electrons lost from the respective MT sphere
is also listed in this tag. An example for such an output is provided below. It features
and states with very high lying eigenenergies.
<coreStates atomType=" 1" atomicNumber=" 23" spin="1" kinEnergy=" 941.0636778793" eigValSum=" -550.9805159504" lostElectrons=" 0.111893"> <state n="1" l="0" j="0.5" energy="-195.9388108744" weight="2.000"/> <state n="2" l="0" j="0.5" energy="-21.4169509005" weight="2.000"/> <state n="2" l="1" j="0.5" energy="-17.9790788510" weight="2.000"/> <state n="2" l="1" j="1.5" energy="-17.7189379876" weight="4.000"/> <state n="3" l="0" j="0.5" energy="-1.8913495403" weight="2.000"/> <state n="3" l="1" j="0.5" energy="-0.9625902671" weight="2.000"/> <state n="3" l="1" j="1.5" energy="-0.9318007834" weight="4.000"/> </coreStates>
After identifying the core electron states to be moved to the valence description the number of electrons in these states has to be counted. This is done by multiplying for each state the electrons in it by the number of atoms in the respective atom group and adding these numbers up for all considered states of all considered atom groups.
For each atom type and each state the number of core electrons per atom is provided in
In general these are 2 electrons for states, 6 electrons for states, 10 electrons for states, and
14 electrons for states if spin-orbit splitting is neglected.
To move the description of the semicore electrons from the core electrons to the valence electrons the respective core electron states have to be removed in the input file and the number of valence electrons has to be increased.
In the Fleur input file the number of core electron states is provided for each atom species in
The number takes into account the spin-orbit splitting of the core states. This implies that for the transfer of states the number
has to be reduced by 1 while for , , and states it has to be reduced by 2. If the electron configuration is directly
provided in an
electronConfig tag the respective states listed in
to be moved directly to the section of the valence electrons in
atomSpecies/species/electronConfig/valenceConfig. The number
of valence electrons is specified in
calculationSetup/bzIntegration/@valenceElectrons. It has to be adapted even if the electron
configuration is specified directly.
The last step is the extension of the LAPW basis by local orbitals (LOs). For this you have to consider the main quantum number of the semicore states and the orbital character.
For the addition of semicore LOs (SCLOs) a new
lo tag has to be inserted in the
atomSpecies/species section. All of these
tags have to be at the end of the section. The tag involves the specification of the LO type in
atomSpecies/species/lo/@type. For the
description of LOs this has to be set to
SCLO. It specifies details of the LO energy parameter calculation procedure.
the spherical effective MT potential by a confining potential outside the MT sphere, considers an atomic problem with this potential, and uses
the eigenenergy related to the specified main quantum number and angular momentum quantum number as LO energy parameter. The main quantum number
is specified in
atomSpecies/species/lo/@n and the angular momentum quantum number in
atomSpecies/species/lo/@l. The last
parameter that has to be specified in this tag is the degree of the energy derivative of the solution to the atomic problem. This
is specified in
atomSpecies/species/lo/@eDeviv. For the most common usage of the function this
has to be set to 0. If higher order energy derivatives of the function have to be used the respective degree of the derivative has to be specified
here. An example for the specififaction of semicore LOs is shown below.
<lo type="SCLO" l="1" n="3" eDeriv="0"/>