Structure and magnetism of Cr2BP3O12: Towards the quantum-classical crossover in a spin-3/2 alternating chain

Magnetic properties of the spin-3/2 Heisenberg system Cr2BP3O12 are investigated by magnetic susceptibility chi(T) measurements, electron spin resonance, neutron diffraction, and density functional theory (DFT) calculations, as well as classical and quantum Monte Carlo (MC) simulations. The broad maximum of chi(T) at 85K and the antiferromagnetic Weiss temperature of 139 K indicate low-dimensional magnetic behavior. Below TN = 28 K, Cr2BP3O12 is antiferromagnetically ordered with the k = 0 propagation vector and an ordered moment of 2.5 muB/Cr. DFT calculations, including DFT+U and hybrid functionals, yield a microscopic model of spin chains with alternating nearest-neighbor couplings J1 and J1' . The chains are coupled by two inequivalent interchain exchanges of similar strength (~1-2 K), but different sign (antiferromagnetic and ferromagnetic). The resulting spin lattice is quasi-one-dimensional and not frustrated. Quantum MC simulations show excellent agreement with the experimental data for the parameters J1 ~= 50 K and J1'/J1 ~= 0.5. Therefore, Cr2BP3O12 is close to the gapless critical point (J1'/J1 = 0.41) of the spin-3/2 bond-alternating Heisenberg chain. The applicability limits of the classical approximation are addressed by quantum and classical MC simulations. Implications for a wide range of low-dimensional S = 3/2 materials are discussed.Comment: Published version: 13 pages, 7 figures, 5 tables + Supplementary informatio

(C2H10N2)[BPO4F2]-Structural relations between [BPO4F2]2- and [Si2O6]4-

Colourless crystals of (C2H10N2)[BPO4F2] were prepared from mixture of ethylendiamine, H3BO3, BF3 . C2H5NH2, H3PO4 and HCl under mild hydrothermal conditions (220 degreesC). The crystal structure was determined by single crystal methods (triclinic, P! (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, alpha = 86.08(1)degrees, beta = 88.52(2)degrees, gamma = 71.74(1)degrees, Z = 2) and contains infinite tetrahedral zweier-single-chains (1)(infinity){[BPO4F2](2-)} which are isoelectronic (48e(-)) with the polyanions (1)(infinity){[Si2O6](4-)} of the pyroxene family

Crystal structure of the 1M-modification of caesium gallium(Ⅲ) monohy-drogen triphosphate, 1M-CsGaHP3O10

CsGaHO10P3, monoclinic, P12(1)/n1 (No. 13), a = 8.843(1) Angstrom, b = 4.9523(5) Angstrom, c = 11.084(1) Angstrom,beta = 108.793(6)degrees, V = 459.5 Angstrom(3), Z = 2, R-gt(F) = 0.042, wR(ref)(F-2) = 0.123, T = 295 K

(C6H14N2){Zn[ZnB2P4O15(OH)2]· (C6H13N2)Cl}_ A new templated zincoborophosphate

Colorless crystals of (C6H14N2){Zn[ZnB2P4O15(OH)(2)].(C6H13N2)Cl} (1) were prepared from mixtures of ZnCl2, B2O3, diaza-bicyclo[2.2.2] octane (DABCO), and 85% H3PO4 under mild hydrothermal conditions (170 degreesC). The crystal structure was determined by single-crystal X-ray diffraction (monoclinic, P2(1)/c (No. 14), a = 1704.3(1) pm, b = 937.03(5) pm, c = 1619.75(8) pro, beta = 96.894(3)degrees, Z = 2). The crystal structure contains tetrahedral zigzag ribbons, [ZnB2P4O15(OH)(2)](4-)}, running along [010]. Additional ZnO2NCl tetrahedra at the borders complete the ribbons by sharing common O-corners with the zincoborophosphate polymer. The nitrogen atoms of the quaternary ZnO2NCl tetrahedra belong to monoprotonated (HDABCO)(+) ions. A second (diprotonated) species, (H(2)DABCO)(2+), acts as a pure template and is fixed to adjacent zincoborophosphate ribbons along [100] via hydrogen bonds. The title compound 1 can be described as an adduct of (C6H14N2){Zn [ZnB2P4O15(OH)(2)]} with diaza-bicyclo[2.2.2]octane-hydrochloride. Thermoanalytical and X-ray powder diffraction investigations to high temperatures (740 degreesC) show the decomposition of 1 and the formation of a NH4[ZnBP2O8] polymorph as an intermediate

Crystal structure of dichromium monoborotriphosphate, Cr2[BP3O12]

A considerable number of borophosphates has been characterized in the past six years [1, 2]; however no chromium based compounds have been reported so far. The title compound was synthesized by high temperature reaction (1273 K) of mixtures of Cr2O3 with BPO4 (molar ratio 1:3) and CrPO4 . 4H(2)O with BPO4 . xH(2)O (molar ratio 2 : 1), respectively. The syntheses were carried out under air. The starting materials were of analytical grade, The crystal structure was solved by direct methods from X-ray powder data and refined by Rietveld methods [3-5], The chemical composition was confirmed by ICP-AES analysis

Crystal structure of caesium gallium(III) catena-[monohydrogen-monoborate-bis(monophosphate)], CsGa[BP2O8(OH)]

BCsGaHO9P2, monoclinic, P12(1)/c1 (No. 14), a = 9.259(1) Angstrom b = 8.6462(9) Angstrom, c = 9.615(1) Angstrom,beta = 103.059(6)degrees, V = 749.8 Angstrom(3), Z = 4, R-gt(F) = 0.050, wR(ref)(F-2) = 0.104, T = 295 K

Cu-II materials - From crystal chemistry to magnetic model compounds

Based on electronic structure calculations within the density functional theory, we report a systematic approach for the modelling of low-dimensional Cu-II materials. Combining concepts of crystal chemistry with ab initio-based magnetic models, we present a systematic study of recently discovered compounds. Our calculation results are in good agreement with thermodynamic and magnetic measurements, suggesting the presented approach as a well-directed route to explore the magnetic phase diagram of low-dimensional Cu-II systems. (c) 2007 NIMS and Elsevier Ltd. All rights reserved

Analysis of sexual phenotype and prezygotic fertility in natural populations of Fucus spiralis, F. vesiculosus (Fucaceae, Phaeophyceae) and their putative hybrids

In the genus Fucus, the character dioecy/hermaphroditism has undergone multiple state changes and hybridization is possible between taxa with contrasting mating systems, e.g. between the dioecious Fucus vesiculosus and the hermaphrodite F. spiralis. In the context of mating system evolution, we evaluated the potential consequences of hybridization by studying the variation in sexual phenotype and prezygotic fertility. Firstly, as a result of hybridization between the two sexual systems, gender variation may arise depending on the relative importance of genes with large versus small phenotypic effects. We thus qualitatively examined the extent of gender variation within and among individual hybrids in comparison with both parental species. Secondly, if hybridization breaks up co-adapted gene complexes, hybrid fertility may be reduced in comparison with both parental species. Therefore, we also quantified male and female prezygotic fertility in parental species and their hybrids in order to test for reduction in hybrid fitness. A total of 89 sexually mature individuals (20 F. spiralis, 40 F. vesiculosus, 10 hermaphrodite hybrids and 19 dioecious hybrids) were sampled in two geographically distant regions (France and Portugal) and six conceptacles per individual were observed. Within-individual variation was very restricted qualitatively – only one hybrid carried a conceptacle with a different sexual phenotype from the five others – as well as quantitatively. This suggests a simple genetic system for sex determination involving a few genes with major effects. In addition, analyses showed no significant decrease in hybrid fertility compared with parental species. Moreover, hybrids exhibited all sexual phenotypes, suggesting several generations of hybridization and backcrossing and, therefore, that hybrids are reproductively successful. Finally, the occurrence of sterile paraphyses in female and hermaphrodite individuals was interpreted as a relic of male function and suggests that, as in higher plants, evolution from hermaphroditism to dioecy may be the most parsimonious pathway