X-ray diffraction measurements of Mo melting to 119 GPa and the high pressure phase diagram

In this paper, we report angle-dispersive X-ray diffraction data of molybdenum melting, measured in a double-sided laser-heated diamond-anvil cell up to a pressure of 119 GPa and temperatures up to 3400 K. The new melting temperatures are in excellent agreement with earlier measurements up to 90 GPa that relied on optical observations of melting and in strong contrast to most theoretical estimates. The X-ray measurements show that the solid melts from the bcc structure throughout the reported pressure range and provide no evidence for a high temperature transition from bcc to a close-packed structure, or to any other crystalline structure. This observation contradicts earlier interpretations of shock data arguing for such a transition. Instead, the values for the Poisson ratios of shock compressed Mo, obtained from the sound speed measurements, and the present X-ray evidence of loss of long-range order suggest that the 210 GPa ( ∼ 4100 K) transition in the shock experiment is from the bcc structure to a new, highly viscous, structured [email protected]

High-pressure study of the behavior of mineral barite by X-ray diffraction

In this paper, we report the angle-dispersive x-ray diffraction data of barite, BaSO 4, measured in a diamond-anvil cell up to a pressure of 48 GPa, using three different fluid pressure-transmitting media (methanol-ethanol mixture, silicone oil, and He). Our results show that BaSO 4 exhibits a phase transition at pressures that range from 15 to 27 GPa, depending on the pressure media used. This indicates that nonhydrostatic stresses have a crucial role in the high-pressure behavior of this compound. The new high-pressure (HP) phase has been solved and refined from powder data, having an orthorhombic P2 12 12 1 structure. The pressure dependence of the structural parameters of both room- and HP phases of BaSO 4 is also discussed in light of our theoretical first-principles total-energy calculations. Finally, a comparison between the different equations of state obtained in our experiments is reported. © 2011 American Physical Society.Financial support from the Spanish Consolider Ingenio 2010 Program (Project No. CDS2007-00045) is acknowledged. The work was also supported by Spanish MICCIN under Projects No. CTQ2009-14596-C02-01 and No. MAT2010-21270-C04-01 as well as from Comunidad de Madrid and European Social Fund: S2009/PPQ-1551 4161893 (QUIMAPRES). The ESRF is acknowledged for provision of beamtime.Santamaría-Pérez, D.; Gracia, L.; Garbarino, G.; Beltrán, A.; Chuliá-Jordán, R.; Gomis Hilario, O.; Errandonea, D.... (2011). High-pressure study of the behavior of mineral barite by X-ray diffraction. Physical Review B. 84:54102-1-54102-8. https://doi.org/10.1103/PhysRevB.84.054102S54102-154102-884RUBIN, A. E. (1997). Mineralogy of meteorite groups. Meteoritics & Planetary Science, 32(2), 231-247. doi:10.1111/j.1945-5100.1997.tb01262.xVegas, A. (2000). Cations in Inorganic Solids. Crystallography Reviews, 7(3), 189-283. doi:10.1080/08893110008044245Santamaría-Pérez, D., & Vegas, A. (2003). The Zintl–Klemm concept applied to cations in oxides. I. The structures of ternary aluminates. Acta Crystallographica Section B Structural Science, 59(3), 305-323. doi:10.1107/s0108768103005615Vegas, A., & Jansen, M. (2001). Structural relationships between cations and alloys; an equivalence between oxidation and pressure. Acta Crystallographica Section B Structural Science, 58(1), 38-51. doi:10.1107/s0108768101019310Lee, P.-L., Huang, E., & Yu, S.-C. (2001). Phase diagram and equations of state of BaSO4. High Pressure Research, 21(2), 67-77. doi:10.1080/08957950108201005Lee, P.-L., Huang, E., & Yu, S.-C. (2003). High-pressure Raman and X-ray studies of barite, BaSO4. High Pressure Research, 23(4), 439-450. doi:10.1080/0895795031000115439Crichton, W. A., Merlini, M., Hanfland, M., & Muller, H. (2011). The crystal structure of barite, BaSO4, at high pressure. American Mineralogist, 96(2-3), 364-367. doi:10.2138/am.2011.3656Errandonea, D., Santamaria-Perez, D., Bondarenko, T., & Khyzhun, O. (2010). New high-pressure phase of HfTiO4 and ZrTiO4 ceramics. Materials Research Bulletin, 45(11), 1732-1735. doi:10.1016/j.materresbull.2010.06.061López-Solano, J., Rodríguez-Hernández, P., Muñoz, A., Gomis, O., Santamaría-Perez, D., Errandonea, D., … Raptis, C. (2010). Theoretical and experimental study of the structural stability ofTbPO4at high pressures. Physical Review B, 81(14). doi:10.1103/physrevb.81.144126Hammersley, A. P., Svensson, S. O., Hanfland, M., Fitch, A. N., & Hausermann, D. (1996). Two-dimensional detector software: From real detector to idealised image or two-theta scan. High Pressure Research, 14(4-6), 235-248. doi:10.1080/08957959608201408Mao, H. K., Xu, J., & Bell, P. M. (1986). Calibration of the ruby pressure gauge to 800 kbar under quasi-hydrostatic conditions. Journal of Geophysical Research, 91(B5), 4673. doi:10.1029/jb091ib05p04673Rodríguez-Carvajal, J. (1993). Recent advances in magnetic structure determination by neutron powder diffraction. Physica B: Condensed Matter, 192(1-2), 55-69. doi:10.1016/0921-4526(93)90108-iBecke, A. D. (1993). Density‐functional thermochemistry. III. The role of exact exchange. The Journal of Chemical Physics, 98(7), 5648-5652. doi:10.1063/1.464913Lee, C., Yang, W., & Parr, R. G. (1988). Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Physical Review B, 37(2), 785-789. doi:10.1103/physrevb.37.785Gracia, L., Beltrán, A., & Andrés, J. (2007). Characterization of the High-Pressure Structures and Phase Transformations in SnO2. A Density Functional Theory Study. The Journal of Physical Chemistry B, 111(23), 6479-6485. doi:10.1021/jp067443vGracia, L., Beltrán, A., & Errandonea, D. (2009). Characterization of theTiSiO4structure and its pressure-induced phase transformations: Density functional theory study. Physical Review B, 80(9). doi:10.1103/physrevb.80.094105Blanco, M. A., Francisco, E., & Luaña, V. (2004). GIBBS: isothermal-isobaric thermodynamics of solids from energy curves using a quasi-harmonic Debye model. Computer Physics Communications, 158(1), 57-72. doi:10.1016/j.comphy.2003.12.001Errandonea, D., Santamaría-Perez, D., Vegas, A., Nuss, J., Jansen, M., Rodríguez-Hernandez, P., & Muñoz, A. (2008). Structural stability ofFe5Si3andNi2Sistudied by high-pressure x-ray diffraction andab initiototal-energy calculations. Physical Review B, 77(9). doi:10.1103/physrevb.77.094113Santamarı́a-Pérez, D., Nuss, J., Haines, J., Jansen, M., & Vegas, A. (2004). Iron silicides and their corresponding oxides: a high-pressure study of Fe5Si3. Solid State Sciences, 6(7), 673-678. doi:10.1016/j.solidstatesciences.2004.03.027Errandonea, D., Meng, Y., Somayazulu, M., & Häusermann, D. (2005). Pressure-induced transition in titanium metal: a systematic study of the effects of uniaxial stress. Physica B: Condensed Matter, 355(1-4), 116-125. doi:10.1016/j.physb.2004.10.030Klotz, S., Paumier, L., Le March, G., & Munsch, P. (2009). The effect of temperature on the hydrostatic limit of 4:1 methanol–ethanol under pressure. High Pressure Research, 29(4), 649-652. doi:10.1080/08957950903418194Errandonea, 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.2008.02.001Lacomba-Perales, R., Errandonea, D., Meng, Y., & Bettinelli, M. (2010). High-pressure stability and compressibility ofAPO4(A=La, Nd, Eu, Gd, Er, and Y) orthophosphates: An x-ray diffraction study using synchrotron radiation. Physical Review B, 81(6). doi:10.1103/physrevb.81.064113Crichton, W. A., Parise, J. B., Antao, S. M., & Grzechnik, A. (2005). Evidence for monazite-, barite-, and AgMnO4(distorted barite)-type structures of CaSO4at high pressure and temperature. American Mineralogist, 90(1), 22-27. doi:10.2138/am.2005.1654Huang, T., Shieh, S. R., Akhmetov, A., Liu, X., Lin, C.-M., & Lee, J.-S. (2010). Pressure-induced phase transition inBaCrO4. Physical Review B, 81(21). doi:10.1103/physrevb.81.214117Zhang, F. X., Wang, J. W., Lang, M., Zhang, J. M., Ewing, R. C., & Boatner, L. A. (2009). High-pressure phase transitions ofScPO4andYPO4. Physical Review B, 80(18). doi:10.1103/physrevb.80.184114Panchal, V., Garg, N., & Sharma, S. M. (2006). Raman and x-ray diffraction investigations on BaMoO4under high pressures. Journal of Physics: Condensed Matter, 18(16), 3917-3929. doi:10.1088/0953-8984/18/16/00

Polymorphs by Pressure

Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEpu

Zircon to monazite phase transition in CeVO4

X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 and 16 GPa, respectively. Experiments reveal that at 5.3 GPa the onset of a pressure-induced irreversible phase transition from the zircon to the monazite structure. Beyond this pressure, diffraction peaks and Raman-active modes of the monazite phase are measured. The zircon to monazite transition in CeVO4 is distinctive among the other rare-earth orthovanadates. We also observed softening of external translational Eg and internal B2g bending modes. We attributed it to mechanical instabilities of zircon phase against the pressure-induced distortion. We additionally report lattice-dynamical and total-energy calculations which are in agreement with the experimental results. Finally, the effect of non-hydrostatic stresses on the structural sequence is studied and the equations of state of different phases are reported.Comment: 45 pages, 8 figures, 8 table

Phase stability of stress-sensitive Ag2CO3 silver carbonate at high pressures and temperature

Silver carbonate (Ag2CO3) is a material currently used for artificial carbon storage. In this work, we report synchrotron X-ray powder diffraction (XRD) experiments under high pressure and high temperature in combination with density-functional theory (DFT) calculations on silver carbonate up to 13.3 GPa. Two pressure-induced phase transitions were observed at room temperature: at 2.9 GPa to a high-pressure (HP1) phase and at 10.5 GPa to a second high-pressure phase (HP2). The facts that a) the HP2 phase can be indexed with the initial P21/m structure, b) our DFT calculations predict the initial structure is stable in the entire pressure range, and c) the HP2 phase is stable under decompression suggest that the intermediate HP1 phase is a product of the appearance of non-hydrostatic stresses in the sample. The observed structural transformations are associated to a high sensitivity of this compound to non-hydrostatic conditions. The compressibility of Ag2CO3 has also been determined, showing the c axis is the most compressible and that the bulk modulus increases quickly with applied pressure. We attribute both observations to the weak nature of the closed-shell Ag–Ag interactions in this material. The behavior of Ag2CO3 under heating at approximately 3 GPa was also studied. No temperature-induced phase transitions were found at this pressure, and the thermal expansion was determined to be relatively high for a carbonate.Authors thank the financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) and the Agencia Estatal de Investigación under projects MALTA Consolider Ingenio 2010 network (RED2018-102612-T) and PGC2021-125518NB-I00 (cofinanced by EU FEDER funds), and from the Generalitat Valenciana under projects CIAICO/2021/241 and MFA/2022/007. A.O.R. acknowledges the financial support of the Spanish MINECO RyC-2016-20301 Ramón y Cajal Grant and the project AYUD/2021/51036 of the Principality of Asturias (cofinanced by EU FEDER funds). Authors also thank the MALTA Consolider supercomputing centre and Compute Canada for computational resources and ALBA-CELLS synchrotron for providing beamtime under experiments 2020084419 and 2021024988. These experiments were performed at the MSPD beamline with the collaboration of ALBA staff

Phase stability and dense polymorph of the BaCa(CO3)2 barytocalcite carbonate

The double carbonate BaCa(CO3)2 holds potential as host compound for carbon in the Earth?s crust and mantle. Here, we report the crystal structure determination of a high-pressure BaCa(CO3)2 phase characterized by single-crystal X-ray diffraction. This phase, named post-barytocalcite, was obtained at 5.7 GPa and can be described by a monoclinic Pm space group. The barytocalcite to post-baritocalcite phase transition involves a significant discontinuous 1.4% decrease of the unit-cell volume, and the increase of the coordination number of 1/4 and 1/2 of the Ba and Ca atoms, respectively. High-pressure powder X-ray diffraction measurements at room- and high-temperatures using synchrotron radiation and DFT calculations yield the thermal expansion of barytocalcite and, together with single-crystal data, the compressibility and anisotropy of both the low- and high-pressure phases. The calculated enthalpy differences between different BaCa(CO3)2 polymorphs confirm that barytocalcite is the thermodynamically stable phase at ambient conditions and that it undergoes the phase transition to the experimentally observed post-barytocalcite phase. The double carbonate is significantly less stable than a mixture of the CaCO3 and BaCO3 end-members above 10 GPa. The experimental observation of the high-pressure phase up to 15 GPa and 300 ºC suggests that the decomposition into its single carbonate components is kinetically hindered.Authors thank the fnancial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) and the Agencia Estatal de Investigación under projects MALTA Consolider Ingenio 2010 network (RED2018-102612-T), PID2019-106383GB-C44, FIS2017-83295-P and PGC2018-097520-A-I00 (cofnanced by EU FEDER funds), and from the Generalitat Valenciana under project PROMETEO/2018/123. A.O.R. acknowledges the fnancial support of the Spanish MINECO RyC-2016-20301 Ramon y Cajal Grant. Authors also thank Dr. Nicolescu and the Mineralogy and Meteoritic Department of the Yale Peabody Museum of Natural History for providing the mineral samples, the MALTA Consolider supercomputing centre and Compute Canada for computational resources, the General Services of Research Support (SEGAI) at La Laguna University and ALBA-CELLS synchrotron for providing beamtime under experiments 2020084419 and 2021024988. Tese experiments were performed at the MSPD beamline with the collaboration of ALBA staf

Structural and vibrational study of cubic Sb2O3 under high pressure

We report an experimental and theoretical study of antimony oxide (Sb 2O 3) in its cubic phase (senarmontite) under high pressure. X-ray diffraction and Raman scattering measurements up to 18 and 25 GPa, respectively, have been complemented with ab initio total-energy and lattice-dynamics calculations. X-ray diffraction measurements do not provide evidence of a space-group symmetry change in senarmontite up to 18 GPa. However, Raman scattering measurements evidence changes in the pressure coefficients of the Raman mode frequencies at 3.5 and 10 GPa, respectively. The behavior of the Raman modes with increasing pressure up to 25 GPa is fully reproduced by the lattice-dynamics calculations in cubic Sb 2O 3. Therefore, the combined analysis of both experiments and lattice-dynamics calculations suggest the occurrence of two isostructural phase transformations at 3.5 and 10 GPa, respectively. Total-energy calculations show that the isostructural phase transformations occur through local atomic displacements in which senarmontite loses its molecular character to become a three-dimensional solid. In addition, our calculations provide evidence that cubic senarmontite cannot undergo a phase transition to orthorhombic valentinite at high pressure, and that a phase transition to a ß-Bi 2O 3-type structure is possible above 25 GPa. © 2012 American Physical Society.Financial support from the Spanish Consolider Ingenio 2010 Program (Project No. CDS2007-00045) is acknowledged. The work was also supported by Spanish MICCIN under Projects No. CTQ2009-14596-C02-01 and No. MAT2010-21270-C04-01/04 as well as from Comunidad de Madrid and European Social Fund, S2009/PPQ-1551 4161893 (QUIMAPRES) and from Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia under projects UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11. Spanish Fundacio Bancaixa Project No. P1-1A2009-08 and Brazilian Capes/Fundacion Carolina (BEX 3939/10-3) are also acknowledged.Pereira, ALJ.; Gracia, L.; Santamaría-Pérez, D.; Vilaplana Cerda, RI.; Manjón Herrera, FJ.; Errandonea, D.; Nalin, M.... (2012). Structural and vibrational study of cubic Sb2O3 under high pressure. Physical Review B. 85(17):174108-1-174108-11. https://doi.org/10.1103/PhysRevB.85.174108S174108-1174108-118517Youk, J. H., Kambour, R. P., & MacKnight, W. J. (2000). Polymerization of Ethylene Terephthalate Cyclic Oligomers with Antimony Trioxide†. Macromolecules, 33(10), 3594-3599. doi:10.1021/ma991838dZabinski, J. S., Donley, M. S., & McDevitt, N. T. (1993). Mechanistic study of the synergism between Sb2O3 and MoS2 lubricant systems using Raman spectroscopy. Wear, 165(1), 103-108. doi:10.1016/0043-1648(93)90378-yGhosh, A., & Chakravorty, D. (1991). Transport properties of semiconducting CuO-Sb2O3-P2O5glasses. Journal of Physics: Condensed Matter, 3(19), 3335-3342. doi:10.1088/0953-8984/3/19/012Gopalakrishnan, P. S., & Manohar, H. (1975). Kinetics and mechanism of the transformation in antimony trioxide from orthorhombic valentinite to cubic senarmontite. Journal of Solid State Chemistry, 15(1), 61-67. doi:10.1016/0022-4596(75)90271-6Zachariasen, W. H. (1932). THE ATOMIC ARRANGEMENT IN GLASS. Journal of the American Chemical Society, 54(10), 3841-3851. doi:10.1021/ja01349a006Matsumoto, A., Koyama, Y., Togo, A., Choi, M., & Tanaka, I. (2011). Electronic structures of dynamically stable As2O3, Sb2O3, and Bi2O3crystal polymorphs. Physical Review B, 83(21). doi:10.1103/physrevb.83.214110Miller, P. J., & Cody, C. A. (1982). Infrared and Raman investigation of vitreous antimony trioxide. Spectrochimica Acta Part A: Molecular Spectroscopy, 38(5), 555-559. doi:10.1016/0584-8539(82)80146-3Svensson, C. (1975). Refinement of the crystal structure of cubic antimony trioxide, Sb2O3. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 31(8), 2016-2018. doi:10.1107/s0567740875006759Wood, C., van Pelt, B., & Dwight, A. (1972). The Optical Properties of Amorphous and Crystalline Sb2O3. Physica Status Solidi (b), 54(2), 701-706. doi:10.1002/pssb.2220540234Nalin, M., Messaddeq, Y., Ribeiro, S. J. L., Poulain, M., Briois, V., Brunklaus, G., … Eckert, H. (2004). Structural organization and thermal properties of the Sb2O3–SbPO4glass system. J. Mater. Chem., 14(23), 3398-3405. doi:10.1039/b406075jOrosel, D., Dinnebier, R. E., Blatov, V. A., & Jansen, M. (2012). Structure of a new high-pressure–high-temperature modification of antimony(III) oxide, γ-Sb2O3, from high-resolution synchrotron powder diffraction data. Acta Crystallographica Section B Structural Science, 68(1), 1-7. doi:10.1107/s0108768111046751Grzechnik, A. (1999). Compressibility and Vibrational Modes in Solid As4O6. 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Unveiling the Chemical and Morphological Features of Sb−SnO2Nanocrystals by the Combined Use of High-Resolution Transmission Electron Microscopy and ab Initio Surface Energy Calculations. Journal of the American Chemical Society, 131(40), 14544-14548. doi:10.1021/ja905896uBecke, A. D. (1993). Density‐functional thermochemistry. III. The role of exact exchange. The Journal of Chemical Physics, 98(7), 5648-5652. doi:10.1063/1.464913Lee, C., Yang, W., & Parr, R. G. (1988). Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Physical Review B, 37(2), 785-789. doi:10.1103/physrevb.37.785Beltrán, A., Gracia, L., & Andrés, J. (2006). Density Functional Theory Study of the Brookite Surfaces and Phase Transitions between Natural Titania Polymorphs. The Journal of Physical Chemistry B, 110(46), 23417-23423. doi:10.1021/jp0643000Grimme, S. (2006). Semiempirical GGA-type density functional constructed with a long-range dispersion correction. 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A ‘click chemistry’ approach to the straightforward synthesis of new 4-aryl-1,2,3-triazolocarbanucleosides

The synthesis and biological evaluation as antiviral agents of a series of racemic 4-aryl-1,2,3- triazolyl carbanucleosides of type (±)-10/(±)-11 related to the broad spectrum antiviral agent ribavirin 1 are described. These compounds were produced using a “click chemistry” strategy starting from readily available protected alcohol 13b. The synthetic approach made use of olefinbased organic reactions for the stereoselective construction of the appropriately functionalized cyclopentane ring moiety followed by copper (I) catalyzed Huisgen 1,3-dipolar cycloaddition of azides and alkynes for the regioselective construction of the heterocyclic triazole moietyThe authors thank the Xunta de Galicia for financial support of this work under Project PGIDT02BTF20305PR. M.D.G. thanks the Xunta de Galicia for financial support under “Programa Isidro Parga Pondal”S

New gamma ray signal from gravitationally boosted neutralinos at the galactic center

We discuss the possibility that colliding dark matter particles in the form of neutralinos may be gravitationally boosted near the supermassive black hole at the Galactic center so that they can have enough collision energy to annihilate into a stau pair. Since in some phenomenologically favored supersymmetric models the mass splitting between the neutralino and the lightest stau, one of the two scalar superpartners of the tau lepton, is a few GeV, this channel may be allowed. In addition, staus can decay only into a tau lepton and another neutralino. We calculate the gamma ray spectrum and flux generated by the tau pair discussing the observability of the obtained features.This work was supported by MultiDark under Grant No. CSD2009-00064 of the Spanish MICINN Consolider-Ingenio 2010 Program. Further support is provided by MICINN Projects No. FPA2011-23781, No. FIS-2009-07238, and No. MICINN-INFN(PG21)AIC-D-2011-0724, ESF-COMPSTAR, and Junta de Andalucia under Grant No. P07FQM02962. M. C. acknowledges the hospitality of the Fundamental Physics Department of University of Salamanca where part of this work was developed. The authors acknowledge J. Cembranos, G. Gomez-Vargas, A. Morselli, R. Lineros, and M. A. Sanchez-Conde for useful discussions

The Influence of Abiotic Environment and Connectivity on the Distribution of Diversity in an Andean Fish Fluvial Network

The distribution of Andean freshwater fishes is the result of the interaction of historical and contemporary factors such as basin geomorphology and the physicochemical characteristics of water bodies. Dramatic changes along river networks due to waterfalls or dams generate abrupt changes in longitudinal slopes that function as ecological barriers to dispersal and thus have an effect on the composition and richness of fish assemblages. We expect the amount of variation in beta diversity along the elevation gradient (between 700 and 3,500 m a.s.l.) of the eastern slope of the Cauca River basin to be explained by changes in the aquatic environment and connectivity among sites. We measured connectivity in terms of the distance along the stream channel between sampling sites considering changes in slope. We used a Generalized Dissimilarity Model (GDM) to evaluate the contribution of connectivity and other water mass characteristics (dissolved oxygen, pH, conductivity, temperature, and elevation) in predicting changes in beta diversity. The GDM models explained 33% of the total deviance in species turnover, suggesting that there are additional variables that have not been considered, such as available habitats along the rivers. Elevation was the variable with the largest relative importance in the model and connectivity explained only seven percent of the total variance when all sites were included. However, when only the sampling sites in the headwater streams were included (the most geographically isolated sites), the GDM models explained 51% of the total deviance and the contribution due to connectivity increased. Isolation of stream headwaters, in conjunction with extreme conditions present at high elevations may influence the fish assemblage turnover. Our results provide evidence that elevation has a strong influence on beta diversity of Andean fish assemblages. Species turnover upstream above 1,200 m a.s.l. is strongly influenced by channel connectivity and there are additional environmental variables that need to be included in the models to improve their prediction power