Systematic prediction of new ferroelectrics in space group R3. I

Abstract

Release 2005/1 of the Inorganic Crystal Structure Database contains 158 entries under the space group R3. The first 81 together with 15 related entries include 52 different structure types, 10 of which represent families that have two or more isostructural members. There are 18 types that satisfy the structural criteria for ferroelectricity with a confidence level that necessarily depends upon the reliability of each structural determination. Among them, (LiTaO3)9.Ta2O5 and the CsCd(NO2) family are known ferroelectrics. The remaining 16 include the high-intensity higher-order harmonic generator II-BaB2O4, not previously recognized as ferroelectric. The other predicted ferroelectrics are Te(OH)6.NaF, the MgSO3.6H2O family, Li3P3O9.3H2O, SeNbF9, Al2(H2PO4)3PO4.6H2O, [Cr(OCN2H4)6].[(Co(NH3)2(NO2)4]3.(H2O)(1.5)], NaZnBr3.5H2O, III-Ag3SI, Tl2S, the Ba3Yb4O9 family, the Fe(10.7)Ru(1.3)As5 family, Sr17Ta10S42, Pb8Sb3 and the Sc7I12C family. Six structures reported in the space group R3 most likely exhibit mirror symmetry, with three experimental confirmations. The other 19 structures are most likely nonpolar, with six experimental confirmations. The capacity for physical property prediction by the remaining ten structures is shown to be in doubt. Thus, 46% of the present 52 inorganic structure types initially determined in the space group R3 and 35% of those currently assigned to R3 more likely exhibit an additional inversion center, mirror or glide plane, strongly exceeding the recently reported error rate of approximately 11% in organic structures.

Arsenic in residential soil and household dust in Cornwall, south west England: potential human exposure and the influence of historical mining

“…13068) and the NHS Health Research Authority National Research Ethics Committee (ref. 13/EE/0234). Sampling units consisted of households selected for having a private water supply as per their participation in a wider study of As exposure in south west England.…”

“…A description of the methods employed in this paper for spatial correlation normalisation has been published in detail. 64 The widespread As contamination resulting from the extensive mining operations in Cornwall's past have been widely reported 12,13,25,27 as well as high concentrations at specic, heavily contaminated locations. 65,66 The utility of the As-specic rened mining dataset generated in this study highlights the importance of individual mining site characteristics in how residential As, and other elemental contamination is distributed in the study region.…”

“…Although concentrations in this highly mineralised region would be expected to be naturally elevated, a history of extensive mining and mineral processing, predominantly of Sn, Cu and As, has resulted in further, widespread anthropogenic contamination. 25 It has been estimated 13 that an area of 722 km 2 (7.9% of the region) is contaminated with As to some extent (>110 As mg per kg was applied as a cutoff in this particular study) in south west England. Contamination may arise from mine tailings of which As concentrations vary depending on ore grade, processing efficiency and the economic cut-off point at which the ore was worth processing (Mitchell and Barr, 1995).…”

“…12 Being a constituent of many sulphide minerals, notably arsenopyrite (FeAsS), As contamination can result from the mining of numerous associated metalliferous ores. 13 Global examples of mining related As contamination include: gold (Au) mining in many parts of Africa (e.g. artisanal mining in Ghana 14,15 ), South America (e.g.…”

High-throughput first-principles search for new ferroelectrics

“…Any insulator known experimentally to have both a polar and a non-polar phase has likely already been recognized as a potential ferroelectric, necessitating a search for new structures of known compounds. However, systematically searching all insulating compounds for possible new phases is too computationally demanding to attempt systematically.In this work, we employ two strategies to identify new ferroelectrics, which we apply to a much larger range of materials than related previous searches [1,10,14,[27][28][29][30][31][32][33][34]. In the first strategy, aimed at finding proper ferroelectrics, we start with a list of experimentally known non-polar transition metal oxides, nitrides, and sulfides, and we perform a Γ-point phonon calculation, looking for materials with unstable polar modes.…”