  New monoclinic ($P2$/$c$) tungstates - a medium-entropy tungstate,
(Mn,Ni,Cu,Zn)WO$_4$, and a high-entropy tungstate, (Mn,Co,Ni,Cu,Zn)WO$_4$ -
were synthesized and characterized. Their phase purity and solid solution
nature were confirmed by powder X-ray diffraction and Raman spectroscopy. X-ray
absorption spectroscopy was used to probe the local structure around metal
cations. The atomic structures based on the ideal solid solution model were
optimized by a simultaneous analysis of the extended X-ray absorption fine
structure spectra at multiple metal absorption edges - five for
(Mn,Ni,Cu,Zn)WO$_4$ and six for (Mn,Co,Ni,Cu,Zn)WO$_4$ - by means of reverse
Monte Carlo simulations. In both compounds, Ni$^{2+}$ ions have the strongest
tendency to organize their local environment and form slightly distorted
[NiO$_6$] octahedra, whereas Mn$^{2+}$, Co$^{2+}$, and Zn$^{2+}$ ions have a
strongly distorted octahedral coordination. The most intriguing result is that
the shape of [CuO$_6$] octahedra in (Mn,Ni,Cu,Zn)WO$_4$ and
(Mn,Co,Ni,Cu,Zn)WO$_4$ differs from that found in pure CuWO$_4$, where a strong
Jahn-Teller distortion is present: [CuO$_6$] octahedra become more regular with
increasing degree of dilution.
