Isotope effects on the lattice parameter of cubic SiC

Path-integral molecular dynamics simulations in the isothermal-isobaric (NPT) ensemble have been carried out to study the dependence of the lattice parameter of 3C-SiC upon isotope mass. This computational method allows a quantitative and nonperturbative study of such anharmonic effect. Atomic nuclei were treated as quantum particles interacting via a tight-binding-type potential. At 300 K, the difference Delta a between lattice parameters of 3C-SiC crystals with 12C and 13C amounts to 2.1 x 10^{-4} A. The effect due to Si isotopes is smaller, and amounts to 3.5 x 10^{-5} A when replacing 28Si by 29Si. Results of the PIMD simulations are interpreted in terms of a quasiharmonic approximation for the lattice vibrations.Comment: 4 pages, 3 figure

Dispersive calculation of complex Regge trajectories for the lightest f_2 resonances and the K^∗(892)

We apply a recently developed dispersive formalism to calculate the Regge trajectories of the f_2(1270), f´_ 2(1525) and K^∗(892) mesons. Trajectories are calculated, not fitted to a family of resonances. Assuming that these resonances can be treated in the elastic approximation, the only input are the pole position and residue of a resonance. In all three cases, the predicted Regge trajectories are almost real and linear, with slopes in agreement with the universal value of order 1 GeV_(−2). We also show how these results barely change when considering more than two subtractions in the dispersive formalism

Post-spinel transformations and equation of state in ZnGa2O4: Determination at high-pressure by in situ x-ray diffraction

Room temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa2O4 undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn2O4. At 55 GPa, a second transition to the orthorhombic marokite structure (CaMn2O4-type) takes place. The equation of state of cubic spinel ZnGa2O4 is determined: V0 = 580.1(9) A3, B0 = 233(8) GPa, B0'= 8.3(4), and B0''= -0.1145 GPa-1 (implied value); showing that ZnGa2O4 is one of the less compressible spinels studied to date. For the tetragonal structure an equation of state is also determined: V0 = 257.8(9) A3, B0 = 257(11) GPa, B0'= 7.5(6), and B0''= -0.0764 GPa-1 (implied value). The reported structural sequence coincides with that found in NiMn2O4 and MgMn2O4.Comment: 20 pages, 4 figures, 2 Table

Borates or phosphates? That is the question

[EN] Chemical nomenclature is perceived to be a closed topic. However, this work shows that the identification of polyanionic groups is still ambiguous and so is the nomenclature for some ternary compounds. Two examples, boron phosphate (BPO4) and boron arsenate (BAsO4), which were assigned to the large phosphate and arsenate families, respectively, nearly a century ago, are explored. The analyses show that these two compounds should be renamed phosphorus borate (PBO4) and arsenic borate (AsBO4). Beyond epistemology, this has pleasing consequences at several levels for the predictive character of chemistry. It paves the way for future work on the possible syntheses of SbBO4 and BiBO4, and it also renders previous structure field maps completely predictive, allowing us to foresee the structure and phase transitions of NbBO4 and TaBO4. Overall, this work demonstrates that quantum mechanics calculations can contribute to the improvement of current chemical nomenclature. Such revisitation is necessary to classify compounds and understand their properties, leading to the main final aim of a chemist: predicting new compounds, their structures and their transformations.This research was partially supported by Spanish MINECO (grant Nos. MAT2015-71070-REDC and MAT2016-75586-C4-2-P, and MALTA Consolider Team RED2018-102612-T) and Generalitat Valenciana (grant No. PROMETEO/2018/123-EFIMAT). J. Contreras-Garci ' a thanks CALSIMLAB (public grant No. ANR-11-LABX-0037-01), overseen by the French National Research Agency (ANR) as part of the Investissements d'Avenir program (grant No. ANR-11-IDEX-0004-02). M. Marque ' s acknowledges support from the ERC grant `Hecate' and computational resources provided by the UKCP consortium under EPSRC grant EP/P022561/1.Contreras-García, J.; Izquierdo-Ruiz, F.; Marqués, M.; Manjón, F. (2020). Borates or phosphates? That is the question. Acta Crystallographica Section A: Foundations and Advances. 76:197-205. https://doi.org/10.1107/S2053273319016826S19720576Abraham, R. H. & Marsden, J. E. (1994). Foundations of Mechanics. Reading: Addison Wesley.Alinger, N. L., Clark, T., Gasteiger, J., Kollman, P. A., Schaefer, H. F. III, Schreiner, P. R. & Schleyer, von R. (1998). Encyclopedia of Computational Chemistry, edited by R. F. W. Bader. Chichester: Wiley.Bader, R. F. W. (1990). Atoms in Molecules, a Quantum Theory. Oxford: Clarendon.Bader, R. F. W. (1994). Principle of stationary action and the definition of a proper open system. Physical Review B, 49(19), 13348-13356. doi:10.1103/physrevb.49.13348Bastide, J. P. (1987). Systématique simplifiée des composés ABX4 (X = O2−, F−) et evolution possible de leurs structures cristallines sous pression. Journal of Solid State Chemistry, 71(1), 115-120. doi:10.1016/0022-4596(87)90149-6Bayer, G. (1972). Thermal expansion of ABO4-compounds with zircon- and scheelite structures. Journal of the Less Common Metals, 26(2), 255-262. doi:10.1016/0022-5088(72)90045-8Blasse, G., & Van Den Heuvel, G. P. M. (1973). Some optical properties of tantalum borate (tabo4), a compound with unusual coordinations. Physica Status Solidi (a), 19(1), 111-117. doi:10.1002/pssa.2210190109Boyd, R. J. & Matta, C. F. (2007). Editors. The Quantum Theory of Atoms in Molecules. From Solid State to DNA and Drug Design. Weinheim: Wiley-VCH.Brill, R., & Debretteville, A. P. (1955). On the chemical bond type in AlPO4. Acta Crystallographica, 8(9), 567-570. doi:10.1107/s0365110x5500176xDachille, F., & Glasser, L. S. D. (1959). High pressure forms of BPO4 and BAsO4; quartz analogues. Acta Crystallographica, 12(10), 820-821. doi:10.1107/s0365110x59002365Dachille, F., & Roy, R. (1959). High-pressure region of the silica isotypes. Zeitschrift für Kristallographie, 111(1-6), 451-461. doi:10.1524/zkri.1959.111.1-6.451Demartin, F., Diella, V., Gramaccioli, C. M., & Pezzotta, F. (2001). Schiavinatoite, (Nb,Ta)BO4, the Nb analogue of behierite. European Journal of Mineralogy, 13(1), 159-165. doi:10.1127/0935-1221/01/0013-0159Depero, L. E., & Sangaletti, L. (1997). Cation Sublattice and Coordination Polyhedra inABO4Type of Structures. Journal of Solid State Chemistry, 129(1), 82-91. doi:10.1006/jssc.1996.7234Errandonea, D., & Manjón, F. J. (2008). Pressure effects on the structural and electronic properties of ABX4 scintillating crystals. Progress in Materials Science, 53(4), 711-773. doi:10.1016/j.pmatsci.2008.02.001Fukunaga, O., & Yamaoka, S. (1979). Phase transformations in ABO 4 type compounds under high pressure. Physics and Chemistry of Minerals, 5(2), 167-177. doi:10.1007/bf00307551Gázquez, J. L., & Ortiz, E. (1984). Electronegativities and hardnesses of open shell atoms. The Journal of Chemical Physics, 81(6), 2741-2748. doi:10.1063/1.447946Geerlings, P., De Proft, F., & Langenaeker, W. (2003). Conceptual Density Functional Theory. Chemical Reviews, 103(5), 1793-1874. doi:10.1021/cr990029pGenoni, A., Bučinský, L., Claiser, N., Contreras‐García, J., Dittrich, B., Dominiak, P. M., … Grabowsky, S. (2018). Quantum Crystallography: Current Developments and Future Perspectives. Chemistry – A European Journal, 24(43), 10881-10905. doi:10.1002/chem.201705952Gibbs, G. V., Cox, D. F., Boisen, M. B., Downs, R. T., & Ross, N. L. (2003). The electron localization function: a tool for locating favorable proton docking sites in the silica polymorphs. Physics and Chemistry of Minerals, 30(5), 305-316. doi:10.1007/s00269-003-0318-2Gramaccioli, C. M. (2000). Un nuovo minerale: la schiavinatoite. Rendiconti Lincei, 11(4), 197-199. doi:10.1007/bf02904665Haines, J., Chateau, C., Léger, J. M., Bogicevic, C., Hull, S., Klug, D. D., & Tse, J. S. (2003). Collapsing Cristobalitelike Structures in Silica Analogues at High Pressure. Physical Review Letters, 91(1). doi:10.1103/physrevlett.91.015503Hazen, R. M., & Finger, L. W. (1979). Bulk modulus-volume relationship for cation-anion polyhedra. Journal of Geophysical Research: Solid Earth, 84(B12), 6723-6728. doi:10.1029/jb084ib12p06723Hazen, R. M., Finger, L. W., & Mariathasan, J. W. E. (1985). High-pressure crystal chemistry of scheelite-type tungstates and molybdates. Journal of Physics and Chemistry of Solids, 46(2), 253-263. doi:10.1016/0022-3697(85)90039-3IUPAC (1970). Nomenclature of Inorganic Solids. Definitive Rules. 3rd ed. London: International Union of Pure and Applied Chemistry.Kniep, R., Gözel, G., Eisenmann, B., Röhr, C., Asbrand, M., & Kizilyalli, M. (1994). Borophosphates—A Neglected Class of Compounds: Crystal Structures of MII[BPO5](MII Ca, Sr) and Ba3[BP3O12]. Angewandte Chemie International Edition in English, 33(7), 749-751. doi:10.1002/anie.199407491Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Lashin, V. E., Khritokhin, N. A., & Andreev, O. V. (2012). Structure maps of ABX4 inorganic compounds. Russian Journal of Inorganic Chemistry, 57(12), 1584-1587. doi:10.1134/s0036023612120133Léger, J. M., Haines, J., Chateau, C., Bocquillon, G., Schmidt, M. W., Hull, S., … Marchand, R. (2001). Phosphorus oxynitride PON, a silica analogue: structure and compression of the cristobalite-like phase; P  - T phase diagram. Physics and Chemistry of Minerals, 28(6), 388-398. doi:10.1007/s002690100161Liu, L. (1982). Phase transformations in MSiO4 compounds at high pressures and their geophysical implications. Earth and Planetary Science Letters, 57(1), 110-116. doi:10.1016/0012-821x(82)90177-7Martín Pendás, A., Costales, A., Blanco, M. A., Recio, J. M., & Luaña, V. (2000). Local compressibilities in crystals. Physical Review B, 62(21), 13970-13978. doi:10.1103/physrevb.62.13970Monkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Mori-Sánchez, P., Pendás, A. M., & Luaña, V. (2001). Polarity inversion in the electron density of BP crystal. Physical Review B, 63(12). doi:10.1103/physrevb.63.125103Muller, O., & Roy, R. (1973). Phase transitions among the ABX4compounds*,1. Zeitschrift für Kristallographie, 138(138), 237-253. doi:10.1524/zkri.1973.138.138.237O’Keeffe, M., & Hyde, B. G. (1976). Cristobalites and topologically-related structures. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 32(11), 2923-2936. doi:10.1107/s0567740876009308Otero-de-la-Roza, A., Blanco, M. A., Pendás, A. M., & Luaña, V. (2009). Critic: a new program for the topological analysis of solid-state electron densities. Computer Physics Communications, 180(1), 157-166. doi:10.1016/j.cpc.2008.07.018Otero-de-la-Roza, A., Johnson, E. R., & Contreras-García, J. (2012). Revealing non-covalent interactions in solids: NCI plots revisited. Physical Chemistry Chemical Physics, 14(35), 12165. doi:10.1039/c2cp41395gPauling, L. (1929). THE PRINCIPLES DETERMINING THE STRUCTURE OF COMPLEX IONIC CRYSTALS. Journal of the American Chemical Society, 51(4), 1010-1026. doi:10.1021/ja01379a006Pauling, L. (1960). The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry, 3rd ed., pp. 543-562. Ithaca: Cornell University Press.Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Rahm, M., Zeng, T., & Hoffmann, R. (2018). Electronegativity Seen as the Ground-State Average Valence Electron Binding Energy. Journal of the American Chemical Society, 141(1), 342-351. doi:10.1021/jacs.8b10246Range, K.-J., Wildenauer, M., & Heyns, A. M. (1988). Extremely Short Non-Bonding Oxygen?Oxygen Distances: The Crystal Structures of NbBO4, NaNb3O8, and NaTa3O8. Angewandte Chemie International Edition in English, 27(7), 969-971. doi:10.1002/anie.198809691Recio, J. M., Franco, R., Martín Pendás, A., Blanco, M. A., Pueyo, L., & Pandey, R. (2001). Theoretical explanation of the uniform compressibility behavior observed in oxide spinels. Physical Review B, 63(18). doi:10.1103/physrevb.63.184101Schulze, G. E. R. (1933). Die Kristallstruktur von BPO4 und BAsO4. Die Naturwissenschaften, 21(30), 562-562. doi:10.1007/bf01503856Scott, H. P., Williams, Q., & Knittle, E. (2001). Ultralow Compressibility Silicate without Highly Coordinated Silicon. Physical Review Letters, 88(1). doi:10.1103/physrevlett.88.015506Shannon, R. D. (1976). Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica Section A, 32(5), 751-767. doi:10.1107/s0567739476001551Stubican, V. S., & Roy, R. (1963). High-pressure scheelite-structure polymorphs of rare-earth vanadates and arsenates. Zeitschrift für Kristallographie, 119(1-2), 90-97. doi:10.1524/zkri.1963.119.1-2.90Vinet, P., Ferrante, J., Smith, J. R. & Rose, J. H. (1986). J. Phys. C: Solid State Phys. L, 19, 467.Vorres, K. S. (1962). Correlating ABO4 compound structures. Journal of Chemical Education, 39(11), 566. doi:10.1021/ed039p566Yang, W., Parr, R. G., & Uytterhoeven, L. (1987). New relation between hardness and compressibility of minerals. Physics and Chemistry of Minerals, 15(2), 191-195. doi:10.1007/bf00308783Zhang, J., Song, L., Sist, M., Tolborg, K., & Iversen, B. B. (2018). Chemical bonding origin of the unexpected isotropic physical properties in thermoelectric Mg3Sb2 and related materials. Nature Communications, 9(1). doi:10.1038/s41467-018-06980-

New high-pressure phase and equation of state of Ce2Zr2O8

In this paper we report a new high-pressure rhombohedral phase of Ce2Zr2O8 observed from high-pressure angle-dispersive x-ray diffraction and Raman spectroscopy studies up to nearly 12 GPa. The ambient-pressure cubic phase of Ce2Zr2O8 transforms to a rhombohedral structure beyond 5 GPa with a feeble distortion in the lattice. Pressure evolution of unit-cell volume showed a change in compressibility above 5 GPa. The unit-cell parameters of the high-pressure rhombohedral phase at 12.1 GPa are ah = 14.6791(3) {\AA}, ch = 17.9421(5) {\AA}, V = 3348.1(1) {\AA}3. The structure relation between the parent cubic (P2_13) and rhombohedral (P3_2) phases were obtained by group-subgroup relations. All the Raman modes of the cubic phase showed linear evolution with pressure with the hardest one at 197 cm-1. Some Raman modes of the high-pressure phase have a non-linear evolution with pressure and softening of one low-frequency mode with pressure is found. The compressibility, equation of state, and pressure coefficients of Raman modes of Ce2Zr2O8 are also reported.Comment: 33 pages, 8 figures, 6 table

Estructura y crecimiento absoluto de una población de Hippolyte inermes Leach 1815 (Decapoda: Caridea) de las praderas de Zostera marina (L.) (Málaga, Sur de España).

The Hippolyte inermis Leach 1815 population from Zostera marina beds in southern Spain showed two recruitment periods that occurred simultaneously for both sexes (from September to December and from April to June), in a size range between 1.67 and 1.90 mm carapace length, due to gonadal activity and eggs hatching in summer and winter. The estimated Von Bertalanffy parameters were used to determine absolute growth and showed that males live for around 8 months and females for around 12 months; consequently, four cohorts for males and 7 to 8 for females can coexist throughout the cycle. The sex ratio favours females throughout the entire life cycle. Data published on the reproductive biology of H. inermis support the idea that this is a protandric hermaphrodite species, though recent studies have revealed that there is no histological proof of hermaphroditic sexuality in adult specimens of this species. The results obtained here indicate that the Cañuelo Beach Hippolyte inermis population has a gonochoric structure. If H. inermis were to have hermaphroditic sexuality, the sex reversal of adult males would occur in a single moult in the size range between 2.42 and 3.22 mm. These new, secondary females would be incorporated into the primary female cohort at practically the same size, although they would be 0.12 to 5.20 months younger. Our results, compared with those from other population studies, suggest that this species has a highly plastic population structure, which seems to be determined by external factors and which varies between the protandric and gonochoric condition, depending on the conditions of the habitat.El estudio de una población de Hippolyte inermis Leach 1815 de fondos de Zostera marina del Sur de España muestra dos periodos de reclutamiento simultáneo para ambos sexos, de septiembre a diciembre y de abril a junio, en un rango de talla de 1.67-1.90 mm como consecuencia de la maduración gonadal y la eclosión de la puesta en verano e invierno. El estudio de los parámetros de Von Bertalanffy muestra que el modelo de crecimiento absoluto es de tipo indeterminado y que los machos viven alrededor de 8 meses, mientras que las hembras son más longevas (12 meses); consecuentemente durante el período de estudiado coexisten 4 cohortes para los machos y 7-8 para las hembras. El estudio de crecimiento poblacional revela que éste viene determinado por el de las hembras, ya que el sex-ratio siempre es a favor de estas últimas. Datos publicados sobre Hippolyte inermis apoyan que se trata de una especie hermafrodita proterándrica, aunque estudios histológicos en adultos no apoyan esta hipótesis. En el caso de la población estudiada, el conjunto de resultados obtenidos justifican sobradamente que se trata de una población gonocórica. Si existiera cambio de sexo en los machos adultos este se produciría en una sola muda, en el rango de talla de 2.42-3.22 mm y estas nuevas hembras se incorporarían a las cohortes de hembras primarias de la talla más o menos similar pero entre 0.12-5.20 meses más jóvenes. Los resultados obtenidos, en comparación con otras poblaciones de otras áreas geográficas, muestran que posiblemente esta especie tenga una estructura y dinámica poblacional muy versátil, pudiéndose manifestar como una especie proterándrica o gonocórica dependiendo de factores externos propios de cada hábitat

Neutron irradiation defects in gallium sulfide : Optical absorption measurements

Gallium sulfide single crystals have been irradiated with different thermal neutron doses. Defects introduced by neutron irradiation turn out to be optically active, giving rise to absorption bands with energies ranging from 1.2 to 3.2 eV. Bands lying in the band-gap exhibit Gaussian shape. Their energies and widths are independent of the irradiation dose, but their intensities are proportional to it. Thermal annealing is completed in two stages, ending at around 500 and 720 K, respectively. Centers responsible for the absorption bands are proposed to be gallium-vacancy-galliuminterstitial complexes in which the distance between the vacancy (acceptor) and the interstitial (donor) determines the energy and intensity of the absorption band, as well as the annealing [email protected]

Contribución al estudio de los hongos que fructifican sobre la familia Pinaceae (Gen. Pinus L.) en Espana (1ª aportación)

In order to determine wether there is any specific group of fungi able to fructify on plant debris from the genus Pinas L., a Sheme of work was made, introducing new signs for it. 8 new taxons are described, being a contribution to the spanish mycological catalogue. The presence in Spain of Ascobolus archeri formely known only in Tasmania (Australia) should be pointed out.Se realiza un ensayo de trabajo para determinar ciertos grupos de hongos específicos o que muestren apetencia a fructificar sobre restos vegetales del género Pinus, introduciendo signos determinados para estos estudios. Resultan nuevas aportaciones al catálogo micológico español los ocho siguientes tazones: Ascobolus arcberi, Coniophorella olivacea, Oidium candicans, Hypboderma argillaceum, Hypboderma pallidum, Hipochnicium eichleri, Galerina autumnalis y Galerina stylifera. De las cuales Ascobolus archeries nueva cita para Europa