Mavlyanovite, Mn₅Si₃: a new mineral species from a lamproite diatreme, Chatkal Ridge, Uzbekistan

Abstract

Mavlyanovite, ideally Mn 5 Si 3 , is a new mineral from a lamproite diatreme close to the upper reaches of the Koshmansay river, Chatkal ridge, Uzbekistan. It occurs together with unnamed manganese siliciphosphide and manganese silicicarbide minerals in round to ovoid segregations, up to 10 cm in diameter, in volcanic glass. Segregations of hexagonal prismatic mavlyanovite up to 1À2 mm occur in interstices in the matrix and tiny inclusions (1À2 mm) of alabandite and khamrabaevite occur within mavlyanovite. It is opaque with a metallic lustre, has a dark-grey streak, is brittle with a conchoidal fracture and a near-perfect basal cleavage. VHN 100 is 1029À1098 kg/mm 2 (Mohs hardness~7). In plane-polarized reflected light, mavlyanovite is a pale-brownish-grey against the accompanying unnamed manganese silicicarbide (white). Reflectance values and colour data are tabulated. Average results of 19 electron microprobe analyses give Mn 70.84, Fe 6.12, Si 22.57, Ti 0.15, P 0.18, total 99.86 wt.% leading to an empirical formula of (Mn 4.66 Fe 0.40 ) 5.06 (Si 2.91 Ti 0.01 P 0.02 ) 2.94 based on 8 a.p.f.u. The calculated density is 6.06 g/cm 3 , (on the basis of the empirical formula and unit-cell parameters from the structure determination). Mavlyanovite is hexagonal (P6 3 /mcm) with a 6.8971(7), c 4.8075(4) Å , V 198.05(3) Å 3 and Z = 2. The structure has been determined and refined to R 1 = 0.017, wR 2 = 0.044, GoF = 1.16. Mavlyanovite is the naturally-occurring analogue of synthetic Mn 5 Si 3 which is the parent aristotype structure of the Nowotny intermetallic phases studied extensively by the material-science community. It is also the Mn-dominant analogue of xifengite Fe 5 Si 3 . The mineral name honours Academician Gani Arifkhanovich Mavlyanov (1910À1988), for his contributions to the understanding of the geology of Uzbekistan.

Low-temperature electronic transport of manganese silicide shell-protected single crystal nanowires for nanoelectronics applications

“…The SAED results agree with the simulated [320] and [210] zone axes of the Mn 5 Si 3 intermetallic compound assuming a hexagonal crystal structure belonging to the P6 3 / mcm space group. We calculate the lattice parameters to a ¼ b ¼ (6.9 AE 0.3)Å (basal plane) and c ¼ (4.9 AE 0.2)Å, in agreement with literature 32. Furthermore, its c-axis is along the nanowire longitudinal direction, as deduced by the angle comparison between the bright-eld TEM image and the [0002] direction in the SAED pattern (Fig.3e and f, respectively).…”

“…Above T 2 ¼ 105 K, the hexagonal crystalline structure belongs to the P6 3 / mcm space group, where Mn1 occupies an equivalent Si site at 4(d) and Mn2 is located at 6(g) site. 32,42 This structure inhibits exchange interaction, leading to a paramagnetic state. When cooling below T 2 , the crystal develops into an orthorhombic structure, which creates an AFM long-range order collinear along the b-axis.…”

Benchmarking Coordination Number Prediction Algorithms on Inorganic Crystal Structures

“…Algorithms exhibit the greatest deviations for Mn 5 Si 3 and CaIn 2 . 11,12 In the case of 12 Overbinding vs. underbinding in separated elemental, binary, and ternary structure test sets…”

“…Machine learning (ML) of materials properties, where descriptions of the coordination environments of atoms can be important, is increasingly becoming an essential tool in the materials discovery process [7][8][9] and has been enabled by the large amounts of data provided by materials databases. [10][11][12] Coordination numbers have been used to predict formation enthalpies, 13 examine magnetic materials, 14 and as the basis of crystal graphs in convolutional graph-based neural networks. 15,16 Automated coordination number determination has also allowed researchers to reassess conventional rules about the crystal structures of materials.…”

Magnetic phase diagram of the solid solution LaMn2(Ge1-xSix)2 (0 ≤ x ≤ 1) unraveled by powder neutron diffraction

“…The sample composition was con rmed by powder X-ray diffraction (PXRD) and revealed, aside from the targeted pseudo ternary, small amounts of impurities for the samples with the composition x = 0, 0.05, 0.33, 0.47 and 0.58, thus resulting in slight deviations of the major phase composition from the nominal one. The following impurities were identi ed: La 2 O 3 [46] in x = 0 [0.92(5) % by mass fraction]; La 9.3 ((Si 1−x Ge x )O 4 ) 6 O 2 [43] in x = 0.05 [0.84(9) % by mass fraction], 0.33 [1.47(8) % by mass fraction] and 0.47 [1.20(9) % by mass fraction]; Mn 5 (Ge 1−x Si x ) 3 [47,48] in x = 0.33 [3.18(13) % by mass fraction] and 0.47 [3.03(14) % by mass fraction]; La 5 (Ge 1−x Si x ) 4 [49] in x = 0.58 [1.49(19) % by mass fraction]. The compositions for the respective LaMn 2 (Ge 1−x Si x ) 2 samples were re ned from the PXRD data and are used throughout the text to identify the samples.…”