  The temperature dependence of the paramagnetic susceptibility of the iron
pnictide superconductor KFe2As2 and its connection with the spectral properties
of that material is investigated by a combination of density functional theory
(DFT) in the local density approximation and dynamical mean-field theory
(DMFT). Unlike other iron pnictide parent compounds where the typical oxidation
state of iron is 2, the formal valence of Fe in KFe2As2 is 2.5, corresponding
to an effective doping with 0.5 hole per iron atom compared to, for example,
BaFe2As2. This shifts the chemical potential and thereby reduces the distance
between the peaks in the spectral functions of KFe2As2 and the Fermi energy as
compared to BaFe2As2. The shift, which is clearly seen on the level of DFT as
well as in DMFT, is further enhanced by the strong electronic correlations in
KFe2As2. In BaFe2As2 the presence of these peaks results [Phys. Rev. B 86,
125124 (2012)] in a temperature increase of the susceptibility up to a maximum
at ~1000 K. While the temperature increase was observed experimentally the
decrease at even higher temperatures is outside the range of experimental
observability. We predict that in KFe2As2 the situation is different. Namely,
the reduction of the distance between the peaks and the Fermi level due to
doping is expected to shift the maximum in the susceptibility to much lower
temperatures, such that the decrease of the susceptibility should become
visible in experiment.
