## 3 Results and Discussion  
### Crystal Structure Analysis, PXRD Patterns, and SEM-EDS Analyses  
The motivation for this work was to analyze how changes in the Cr/Sn and S/Se chemical substitutions influence the structure and physical properties of the CuCr\({}_{2}\)Se\({}_{4}\) endmember. The crystallographic data and atomic positions of cubic CuCr\({}_{1-1}\)Sr\({}_{0.9}\)S\({}_{2-3}\)Se\({}_{1.7}\) are given in Table 1 and Table S1 (see Supplementary Materials), respectively. The refinements were carried out in the \(\mathrm{Fd}\overline{3}\mathrm{m}\) space group. The method we applied to solve the crystal structure was that of a model Cu atom occupying the tetrahedral (A) sites, and Cr and Sn cations occupying the octahedral [B] sites. This model was based on linear functions constraining the Sn, Cu, and Cr atoms at the 16d and 8a sites. The sum of the site occupation factor (SOF) was forced to equal 1 (fully occupied for 16d = (2 \(-\) x)Cr + \(\mathrm{xSn}\). Furthermore, for the chalcogenide site, the sum of the SOF was forced to equal 1 (fully occupied) for 32e = (4 \(-\) y)S + ySe, and the Sn/Cr and S/Se atoms were also constrained to have equivalent atomic displacement parameters (ADPs). The CuCr\({}_{1-1}\)Sn\({}_{0.9}\)S\({}_{2.3}\)Se\({}_{1.7}\) compound crystallized in a normal spinel-type structure and cell parameter **a** had an intermediate value between those of CuCrSnS\({}_{4}\) (10.175 A) [33] and CuCrSnSe\({}_{4}\) (10.672 A) [34], similar to the values reported for mixed spinels (Cu)\({}_{\rm tet}\)[Cr\({}_{2>}\)Sn\({}_{x}\)]\({}_{\rm oct}\)S\({}_{4>}\)Se\({}_{y}\)[13]. The Cu-X (X = Se/S) distance in CuCr\({}_{1-1}\)Sn\({}_{0.9}\)S\({}_{2.3}\)Se\({}_{1.7}\) was 2.3294(8) A, which is intermediate between the Cu-Se bond length in (Cu)\({}_{\rm tet}\)[Cr\({}_{2>}\)Sn\({}_{x}\)]\({}_{\rm oct}\)Se\({}_{4}\) (2.3832-2.3947 A) and the Cu-S bond length in thiospinels (Cu)\({}_{\rm tet}\)[Ti\({}_{1.7}\)M\({}_{0.3}\)]\({}_{\rm oct}\)S\({}_{4}\) (2.2583-2.2737 A) [5]. The Cu-X distance was near to the tetrahedral covalent radii evaluated by [PERSON] [24] for Cu-S (2.313 A). The (Cu)X\({}_{4}\) tetrahedron was ideal with an angle of 109.5\({}^{\circ}\). The [CrSn]\({}_{\rm Oh}\)-X bond distance was 2.5403(5) A, which is comparable to the [Cr/Sn]-Se bond length in (Cu)\({}_{\rm tet}\)[Cr\({}_{2>}\)Sn\({}_{x}\)]\({}_{\rm oct}\)Se\({}_{4}\). The other important structural parameters (bond distances and angles) were as expected and were in acceptable concordance with those of other thiospin and selenospinel compounds. The degree of distortion in the octahedral sites was evaluated using distortion indices published by [PERSON] et al. [35]. The [Cr\({}_{2>}\)Sn\({}_{x}\)]X\({}_{6}\) octahedron showed a \(\sim\)2.0% degree of distortion, which agrees with the octahedral distortions in chaloscopinels already reported in our previous research [5; 6; 13]. The single positional u parameter of the chalcogen atoms (u, u, u), Wyckoff position 32e, of CuCr\({}_{1-1}\)Sn\({}_{0.9}\)S\({}_{2.3}\)Se\({}_{1.7}\), was 0.25484(4), which is comparable to the values found in cubic CuCr\({}_{1-7}\)Sn\({}_{0.3}\)Se\({}_{4}\) and CuCr\({}_{1.5}\)Sn\({}_{0.5}\)Se\({}_{4}\): u = 0.25663(4) and u = 0.25632(3), respectively [6]. From the single-crystal analysis, rational synthesis of CuCr\({}_{2>}\)Sn\({}_{x}\)S\({}_{2.3}\)Se\({}_{1.7}\) and CuCr\({}_{2>}\)Sn\({}_{x}\)S\({}_{1.7}\)-Se\({}_{2.3}\) (x = 0.4, 0.6, and 1.0) powder samples were performed. The SEM backscattered electron images (mapping) and EDS measurements revealed that the chemical compositions of all the powder samples were uniform throughout the scanned region (Figure 1). For example, the experimental results determined a Cu/Cr/Sn/S/Se ratio of approximately 1.1/1.0/0.8/1.8/2.2. No secondary phases or impurity peaks were revealed within the detection limits of this technique.