The Crystal Structures and Powder Diffraction Patterns of the Uranium Tellurides: A Critical Review

Abstract

A critical review of all the reported structures and powder diffraction patterns in the uranium telluride system has been undertaken. Our recommendations are:1. Structures that are correct:• Cubic – UTe: no experimental pattern exists. Retain calculated 15–865.• Cubic – U3Te4: retain poor quality 12-610 but adopt the pattern calculated here.• Cubic U2Te3: no experimental pattern exists. Adopt pattern calculated here.• Orthorhombic UTe2: Adopt the new pattern of Boehme et al.• Monoclinic αUTe3: Adopt the new pattern of Boehme et al.• Orthorhombic βUTe3: Adopt the pattern calculated here.• Orthorhombic UTe5: Adopt the new pattern of Boeheme et al.2. Structures in need of refinement:• Orthorhombic U2Te3: Adopt pattern calculated here over 34-807.• Hexagonal U7Te12: Adopt pattern calculated here but retain 24-1368.• Orthorhombic UTe1.78: Adopt pattern calculated here and retain our modified 21-1404 reported for U4Te7.• Orthorhombic UTe2.5: Adopt pattern calculated here.• Orthorhombic UTe3.4: Accept recent pattern of Boehme et al.3. Phases for which no structures or reliable patterns exist:• Orthorhombic U3Te4: no published pattern.• Tetragonal U3Te5: three patterns 21-1407, 34-766 and 34-896 exist but all are of very poor quality.4. Phases which probably do not exist:• Tetragonal UTe1.77• Tetragonal UTe2• Cubic UTe2• U3Te7 (21-1402)• U3Te8 (21-1406)

Ternary and Quaternary Uranium and Thorium Chalcogenides

“…Despite the 50-year history of research in this area, the field remains remarkably narrow. Binary chalcogenide systems of both U and Th have been discussed in detail, − but only a few ternary systems have been studied in depth. Because most of the work on U and Th chalcogenides was completed before widespread use of single-crystal diffraction techniques, there are several systems for which little or no structural data are available.…”

Characterization of the Binary Uranium and Thorium Tellurides U7Te12 and Th7Te12

“…The X-ray powder diffraction pattern was indexed with the hexagonal unit cell parameters a = 12.309(4) Å and c = 4.242(2) Å, and a reasonable agreement was assured between the diffracted intensities and those calculated using the Th 7 S 12 positional parameters. However, no residual factors were given and later a critical review on the U−Te system also cast some doubt on the validity of this structural model proposed for U 7 Te 12 . Furthermore, to our knowledge no information concerning the formation of the corresponding thorium telluride Th 7 Te 12 has been reported up to now, and only some observations on Th−Te system 9 have indicated the existence of a phase composition around Th 2 Te 3 with hexagonal symmetry.…”

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

“…With comparison to U oxides, the existing U tellurides with well-determined crystal structures are relatively not so abundant. Even so, after a thorough survey on telluride family, about 40 U tellurides come to our attention for exploring the OS population or regularity. − For simplicity, they are divided into three series: binary U–Te, ternary U–Te–O, and ternary or quaternary U–Te–X (X represent one or two element), as detailed in the following section. All periodic spin-polarized DFT calculations are conducted by Vienna ab initio simulation package (VASP) code.…”