Crystal structure refinement of MnTe2, MnSe2, and MnS2: cation-anion and anion–anion bonding distances in pyrite-type structures

Abstract The stability of hauerite (MnS 2 ) as compared to that of pyrite (FeS 2 ) can be explained by the long Mn–S distance and departure from the typical pyrite-type structures. The structural differences of MnX 2 compounds (X=S, Se, and Te) are the result of spin configurations that are different than those of other MX 2 compounds; however, the arrangement of d -electrons and the size of the ions in MnX 2 compounds do not clearly explain why Mn 2+ in MnX 2 does not exist as a low spin state. To investigate the structural differences of MnX 2 compounds, we synthesized single-crystal MnTe 2 and MnSe 2 and performed single-crsytal X-ray diffraction experiments. The single-crystal X-ray diffraction experiments were conducted on MnTe 2 [ a =6.9513(1) Å, u -parameter=0.38554(2), space group Pa 3̅, Z=4], MnSe 2 [ a =6.4275(2) Å, u -parameter=0.39358(2)], MnS 2 [hauerite; a =6.1013(1) Å, u -parameter=0.40105(4), obtained from Osorezan, Aomori, Japan], and FeS 2 [pyrite; a =5.4190(1) Å, u -parameter 0.38484(5), obtained from Kawarakoba, Nagasaki, Japan]. The X-ray intensity datasets of these compounds do not show any evidence of symmetry reduction. In MnS 2 , the S–S distance is 2.0915(8) Å, which is significantly shorter than that of FeS 2 (2.1618(9) Å), and the mean square displacement of S ( U 11 =0.00915(9) Å 2 ) is smaller than that of Mn ( U 11 =0.01137(9) Å 2 ). The thermal vibration characteristics of MnX 2 compounds are significantly different than those of FeS 2 . Based on structural refinement data, we discuss the low spin state of MnX 2 compounds and the structural stability of pyrite-type structures.