High-pressure structural investigation of several zircon-type orthovanadates

Room temperature angle-dispersive x-ray diffraction measurements on zircon-type EuVO4, LuVO4, and ScVO4 were performed up to 27 GPa. In the three compounds we found evidence of a pressure-induced structural phase transformation from zircon to a scheelite-type structure. The onset of the transition is near 8 GPa, but the transition is sluggish and the low- and high-pressure phases coexist in a pressure range of about 10 GPa. In EuVO4 and LuVO4 a second transition to a M-fergusonite-type phase was found near 21 GPa. The equations of state for the zircon and scheelite phases are also determined. Among the three studied compounds, we found that ScVO4 is less compressible than EuVO4 and LuVO4, being the most incompressible orthovanadate studied to date. The sequence of structural transitions and compressibilities are discussed in comparison with other zircon-type oxides.Comment: 34 pages, 2 Tables, 11 Figure

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

Phonons and Colossal Thermal Expansion Behavior of Ag3Co(CN)6 and Ag3Fe(CN)6

Recently colossal positive volume thermal expansion has been found in the framework compounds Ag3Co(CN)6 and Ag3Fe(CN)6. Phonon spectra have been measured using the inelastic neutron scattering technique as a function of temperature and pressure. The data has been analyzed using ab-initio calculations. We find that the bonding is very similar in both compounds. At ambient pressure modes in the intermediate frequency part of the vibrational spectra in the Co compound are shifted to slightly higher energies as compared to the Fe compound. The temperature dependence of the phonon spectra gives evidence for large explicit anharmonic contribution to the total anharmonicity for low-energy modes below 5 meV. We found that modes are mainly affected by the change in the size of unit cell, which in turn changes the bond lengths and vibrational frequencies. Thermal expansion has been calculated via the volume dependence of phonon spectra. Our analysis indicates that Ag phonon modes in the energy range from 2 to 5 meV are strongly anharmonic and major contributors to thermal expansion in both compounds. The application of pressure hardens the low-energy part of the phonon spectra involving Ag vibrations and confirms the highly anharmonic nature of these modes.Comment: 19 pages, 14 figures and one tabl

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

High-pressure study of ScVO4 by Raman scattering and ab initio calculations

We report results of experimental and theoretical lattice-dynamics studies on scandium orthovanadate up to 35 GPa. Raman-active modes of the low-pressure zircon phase are measured up to 8.2 GPa, where the onset of an irreversible zircon-to-scheelite phase transition is detected. Raman-active modes in the scheelite structure are observed up to 16.5 GPa. Beyond 18.2 GPa we detected a gradual splitting of the Eg modes of the scheelite phase, indicating the onset of a second phase transition. Raman symmetries, frequencies, and pressure coefficients in the three phases of ScVO4 are discussed in the light of ab initio lattice-dynamics calculations that support the experimental results. The results on all the three phases of ScVO4 are compared with those previously reported for related orthovanadates.We acknowledge the financial support of the Spanish MCYT under Grants No. MAT2007-65990-C03-01/03, No. MAT2010-21270-C04-01/03/04, and No. CSD2007-00045, and the computation time provided by the Red Espanola de Supercomputacion and the supercomputer Atlante. F.J.M. acknowledges also financial support from "Vicerrectorado de Innovacion y Desarrollo de la UPV" (No. PAID-05-2009 through Project No. UPV2010-0096). Some of the authors are members of the MALTA Consolider Team.Panchal, V.; Manjón Herrera, FJ.; Errandonea, D.; Rodriguez-Hernandez, P.; López-Solano, J.; Muñoz, A.; Achary, S.... (2011). High-pressure study of ScVO4 by Raman scattering and ab initio calculations. Physical Review B. 83(6):641111-1-64111-10. https://doi.org/10.1103/PhysRevB.83.064111S641111-164111-10836Shafi, S. P., Kotyk, M. W., Cranswick, L. M. D., Michaelis, V. K., Kroeker, S., & Bieringer, M. (2009). In Situ Powder X-ray Diffraction, Synthesis, and Magnetic Properties of the Defect Zircon Structure ScVO4−x. Inorganic Chemistry, 48(22), 10553-10559. doi:10.1021/ic900927jMullica, D. F., Sappenfield, E. L., Abraham, M. M., Chakoumakos, B. C., & Boatner, L. A. (1996). Structural investigations of several LnVO4 compounds. Inorganica Chimica Acta, 248(1), 85-88. doi:10.1016/0020-1693(95)04971-1Errandonea, 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.2008.02.001Aldred, A. T. (1984). Cell volumes of APO4, AVO4, and ANbO4 compounds, where A = Sc, Y, La–Lu. Acta Crystallographica Section B Structural Science, 40(6), 569-574. doi:10.1107/s0108768184002718Errandonea, D., Lacomba-Perales, R., Ruiz-Fuertes, J., Segura, A., Achary, S. N., & Tyagi, A. K. (2009). High-pressure structural investigation of several zircon-type orthovanadates. Physical Review B, 79(18). doi:10.1103/physrevb.79.184104López-Solano, J., Rodríguez-Hernández, P., & Muñoz, A. (2009). Ab initiostudy of high-pressure structural properties of the LuVO4and ScVO4zircon-type orthovanadates. High Pressure Research, 29(4), 582-586. doi:10.1080/08957950903417444Manjón, F. J., Rodríguez-Hernández, P., Muñoz, A., Romero, A. H., Errandonea, D., & Syassen, K. (2010). Lattice dynamics ofYVO4at high pressures. Physical Review B, 81(7). doi:10.1103/physrevb.81.075202Wang, X., Loa, I., Syassen, K., Hanfland, M., & Ferrand, B. (2004). Structural properties of the zircon- and scheelite-type phases ofYVO4at high pressure. Physical Review B, 70(6). doi:10.1103/physrevb.70.064109Klotz, S., Chervin, J.-C., Munsch, P., & Le Marchand, G. (2009). Hydrostatic limits of 11 pressure transmitting media. Journal of Physics D: Applied Physics, 42(7), 075413. doi:10.1088/0022-3727/42/7/075413Errandonea, 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.2004.10.030Mao, 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/jb091ib05p04673Kresse, G., & Furthmüller, J. (1996). Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Physical Review B, 54(16), 11169-11186. doi:10.1103/physrevb.54.11169Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Mujica, A., Rubio, A., Muñoz, A., & Needs, R. J. (2003). High-pressure phases of group-IV, III–V, and II–VI compounds. Reviews of Modern Physics, 75(3), 863-912. doi:10.1103/revmodphys.75.863Guedes, I., Hirano, Y., Grimsditch, M., Wakabayashi, N., Loong, C.-K., & Boatner, L. A. (2001). Raman study of phonon modes in ErVO4 single crystals. Journal of Applied Physics, 90(4), 1843-1846. doi:10.1063/1.1384858Garg, A. B., Rao, R., Sakuntala, T., Wani, B. N., & Vijayakumar, V. (2009). Phase stability of YbVO4 under pressure: In situ x-ray and Raman spectroscopic investigations. Journal of Applied Physics, 106(6), 063513. doi:10.1063/1.3223327Santos, C. C., Silva, E. N., Ayala, A. P., Guedes, I., Pizani, P. S., Loong, C.-K., & Boatner, L. A. (2007). Raman investigations of rare earth orthovanadates. Journal of Applied Physics, 101(5), 053511. doi:10.1063/1.2437676Zhang, 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.80.184114Tossell, J. A. (1975). Electronic structures of silicon, aluminum, and magnesium in tetrahedral coordination with oxygen from SCF-X.alpha. MO calculations. Journal of the American Chemical Society, 97(17), 4840-4844. doi:10.1021/ja00850a010Rao, R., Garg, A. B., Sakuntala, T., Achary, S. N., & Tyagi, A. K. (2009). High pressure Raman scattering study on the phase stability of LuVO4. Journal of Solid State Chemistry, 182(7), 1879-1883. doi:10.1016/j.jssc.2009.05.003Duclos, S. J., Jayaraman, A., Espinosa, G. P., Cooper, A. S., & Maines, R. G. (1989). Raman and optical absorption studies of the pressure-induced zircon to scheelite structure transformation in TbVO4 and DyV04. Journal of Physics and Chemistry of Solids, 50(8), 769-775. doi:10.1016/0022-3697(89)90055-3Smirnov, M. B., Mirgorodsky, A. P., Kazimirov, V. Y., & Guinebretière, R. (2008). Bond-switching mechanism for the zircon-scheelite phase transition. Physical Review B, 78(9). doi:10.1103/physrevb.78.094109Flórez, M., Contreras-García, J., Recio, J. M., & Marqués, M. (2009). Quantum-mechanical calculations of zircon to scheelite transition pathways inZrSiO4. Physical Review B, 79(10). doi:10.1103/physrevb.79.104101Rousseau, D. L., Bauman, R. P., & Porto, S. P. S. (1981). Normal mode determination in crystals. Journal of Raman Spectroscopy, 10(1), 253-290. doi:10.1002/jrs.1250100152Mittal, R., Garg, A. B., Vijayakumar, V., Achary, S. N., Tyagi, A. K., Godwal, B. K., … Chaplot, S. L. (2008). Investigation of the phase stability of LuVO4at high pressure using powder x-ray diffraction measurements and lattice dynamical calculations. Journal of Physics: Condensed Matter, 20(7), 075223. doi:10.1088/0953-8984/20/7/075223Manjón, F. J., Errandonea, D., Garro, N., Pellicer-Porres, J., Rodríguez-Hernández, P., Radescu, S., … Muñoz, A. (2006). Lattice dynamics study of scheelite tungstates under high pressure I.BaWO4. Physical Review B, 74(14). doi:10.1103/physrevb.74.144111Manjon, F. J., Errandonea, D., Garro, N., Pellicer-Porres, J., López-Solano, J., Rodríguez-Hernández, P., … Muñoz, A. (2006). Lattice dynamics study of scheelite tungstates under high pressure II.PbWO4. Physical Review B, 74(14). doi:10.1103/physrevb.74.144112Panchal, 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:10.1088/0953-8984/18/16/002Hardcastle, F. D., & Wachs, I. E. (1991). Determination of vanadium-oxygen bond distances and bond orders by Raman spectroscopy. The Journal of Physical Chemistry, 95(13), 5031-5041. doi:10.1021/j100166a025Brown, I. D., & Wu, K. K. (1976). Empirical parameters for calculating cation–oxygen bond valences. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 32(7), 1957-1959. doi:10.1107/s0567740876006869Lacomba-Perales, R., Martinez-García, D., Errandonea, D., Le Godec, Y., Philippe, J., Le Marchand, G., … López-Solano, J. (2010). Experimental and theoretical investigation of the stability of the monoclinicBaWO4-II phase at high pressure and high temperature. Physical Review B, 81(14). doi:10.1103/physrevb.81.144117Tschauner, O., Errandonea, D., & Serghiou, G. (2006). Possible superlattice formation in high-temperature treated carbonaceous MgB2 at elevated pressure. Physica B: Condensed Matter, 371(1), 88-94. doi:10.1016/j.physb.2005.09.042Errandonea, D., Kumar, R. S., Ma, X., & Tu, C. (2008). High-pressure X-ray diffraction study of SrMoO4 and pressure-induced structural changes. Journal of Solid State Chemistry, 181(2), 355-364. doi:10.1016/j.jssc.2007.12.010Errandonea, D., Santamaria-Perez, D., Grover, V., Achary, S. N., & Tyagi, A. K. (2010). High-pressure x-ray diffraction study of bulk and nanocrystalline PbMoO4. Journal of Applied Physics, 108(7), 073518. doi:10.1063/1.3493048Errandonea, 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.2010.06.061Marqués, M., Flórez, M., Recio, J. M., Gerward, L., & Olsen, J. S. (2006). Structure and stability ofZrSiO4under hydrostatic pressure. Physical Review B, 74(1). doi:10.1103/physrevb.74.014104Lacomba-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.81.064113Long, Y. W., Zhang, W. W., Yang, L. X., Yu, Y., Yu, R. C., Ding, S., … Jin, C. Q. (2005). Pressure-induced structural phase transition in CaCrO4: Evidence from Raman scattering studies. Applied Physics Letters, 87(18), 181901. doi:10.1063/1.2117624Long, Y. W., Yang, L. X., Yu, Y., Li, F. Y., Yu, R. C., Ding, S., … Jin, C. Q. (2006). High-pressure Raman scattering and structural phase transition inYCrO4. Physical Review B, 74(5). doi:10.1103/physrevb.74.054110Errandonea, D., Kumar, R. S., Gracia, L., Beltrán, A., Achary, S. N., & Tyagi, A. K. (2009). Experimental and theoretical investigation ofThGeO4at high pressure. Physical Review B, 80(9). doi:10.1103/physrevb.80.094101Gracia, 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.80.094105Errandonea, D. (2007). Landau theory applied to phase transitions in calcium orthotungstate and isostructural compounds. Europhysics Letters (EPL), 77(5), 56001. doi:10.1209/0295-5075/77/56001Errandonea, D., & Manjón, F. J. (2009). On the ferroelastic nature of the scheelite-to-fergusonite phase transition in orthotungstates and orthomolybdates. Materials Research Bulletin, 44(4), 807-811. doi:10.1016/j.materresbull.2008.09.024Errandonea, D., Pellicer-Porres, J., Manjón, F. J., Segura, A., Ferrer-Roca, C., Kumar, R. S., … Aquilanti, G. (2005). High-pressure structural study of the scheelite tungstatesCaWO4andSrWO4. Physical Review B, 72(17). doi:10.1103/physrevb.72.174106Errandonea, D. (2005). High-pressure X-ray diffraction study of EuWO4 to 12 GPa. physica status solidi (b), 242(14), R125-R127. doi:10.1002/pssb.200541334Begun, G. M., Beall, G. W., Boatner, L. A., & Gregor, W. J. (1981). Raman spectra of the rare earth orthophosphates. Journal of Raman Spectroscopy, 11(4), 273-278. doi:10.1002/jrs.1250110411Podor, R. (1995). Raman spectra of the actinide-bearing monazites. European Journal of Mineralogy, 7(6), 1353-1360. doi:10.1127/ejm/7/6/1353Zhang, C. C., Zhang, Z. M., Dai, R. C., Wang, Z. P., Zhang, J. W., & Ding, Z. J. (2010). High-Pressure Raman and Luminescence Study on the Phase Transition of GdVO4:Eu3+ Microcrystals. The Journal of Physical Chemistry C, 114(42), 18279-18282. doi:10.1021/jp106063cVoron’ko, Y. K., Sobol’, A. A., Shukshin, V. E., Zagumennyĭ, A. I., Zavartsev, Y. D., & Kutovoĭ, S. A. (2009). Raman spectroscopic study of structural disordering in YVO4, GdVO4, and CaWO4 crystals. Physics of the Solid State, 51(9), 1886-1893. doi:10.1134/s1063783409090200Baran, E. J., Escobar, M. E., Fournier, L. L., & Filgueira, R. R. (1981). Die Raman-Spektren der Orthovanadate der Seltenen Erden. Zeitschrift f�r anorganische und allgemeine Chemie, 472(1), 193-199. doi:10.1002/zaac.19814720123Frost, R. L., Henry, D. A., Weier, M. L., & Martens, W. (2006). Raman spectroscopy of three polymorphs of BiVO4: clinobisvanite, dreyerite and pucherite, with comparisons to (VO4)3-bearing minerals: namibite, pottsite and schumacherite. Journal of Raman Spectroscopy, 37(7), 722-732. doi:10.1002/jrs.1499Blin, J. L., Lorriaux-Rubbens, A., Wallart, F., & Wignacourt, J. P. (1996). Synthesis and structural investigation of the Eu1–xBixVO4scheelite phase: X-ray diffraction, Raman scattering and Eu3+luminescence. J. Mater. Chem., 6(3), 385-389. doi:10.1039/jm9960600385Manjón, F. J., Errandonea, D., López-Solano, J., Rodríguez-Hernández, P., & Muñoz, A. (2009). Negative pressures in CaWO4 nanocrystals. Journal of Applied Physics, 105(9), 094321. doi:10.1063/1.3116727Tokunaga, S., Kato, H., & Kudo, A. (2001). Selective Preparation of Monoclinic and Tetragonal BiVO4with Scheelite Structure and Their Photocatalytic Properties. Chemistry of Materials, 13(12), 4624-4628. doi:10.1021/cm0103390Rice, C. E., & Robinson, W. R. (1976). Lanthanum orthovanadate. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 32(7), 2232-2233. doi:10.1107/s0567740876007450Errandonea, D., Manjón, F. J., Somayazulu, M., & Häusermann, D. (2004). Effects of pressure on the local atomic structure of CaWO4 and YLiF4: mechanism of the scheelite-to-wolframite and scheelite-to-fergusonite transitions. Journal of Solid State Chemistry, 177(4-5), 1087-1097. doi:10.1016/j.jssc.2003.10.01

High-Temperature Phonon Spectra of Multiferroic BiFeO3 from Inelastic Neutron Spectroscopy

We report inelastic neutron scattering measurements of the phonon spectra in a pure powder sample of the multiferroic material BiFeO3. A high-temperature range was covered to unravel the changes in the phonon dynamics across the Neel (T_N ~ 650 K) and Curie (T_C ~ 1100 K) temperatures. Experimental results are accompanied by ab-initio lattice dynamical simulations of phonon density of states to enable microscopic interpretations of the observed data. The calculations reproduce well the observed vibrational features and provide the partial atomic vibrational components. Our results reveal clearly the signature of three different phase transitions both in the diffraction patterns and phonon spectra. The phonon modes are found to be most affected by the transition at the T_C. The spectroscopic evidence for the existence of a different structural modification just below the decomposition limit (T_D ~ 1240 K) is unambiguous indicating strong structural changes that may be related to oxygen vacancies and concomitant Fe3+ to Fe2+ reduction and spin transition

Experimental and theoretical investigations on structural and vibrational properties of melilite-type Sr2ZnGe2O7 at high pressure and delineation of a high pressure monoclinic phase

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b00937"We report a combined experimental and theoretical study of melilite-type germanate, Sr2ZnGe2O7, under compression. In situ high-pressure X-ray diffraction and Raman scattering measurements up to 22 GPa were complemented with first-principles theoretical calculations of structural and lattice dynamics properties. Our experiments show that the tetragonal structure of Sr2ZnGe2O7 at ambient conditions transforms reversibly to a monoclinic phase above 12.2 Gpa with similar to 1% volume drop at the phase transition pressure. Density functional calculations indicate the transition pressure at, similar to 13 GPa, which agrees well with the experimental value. The structure of the high-pressure monoclinic phase is closely related to the ambient pressure phase and results from a displacive-type phase transition. Equations of state of both tetragonal and monoclinic phases are reported. Both of the phases show anisotropic compressibility with a larger compressibility in the direction perpendicular to the [ZnGe2O7](2-) sheets than along the sheets. Raman-active phonons of both the tetragonal and monoclinic phases and their pressure dependences were also determined. Tentative assignments of the Raman modes of the tetragonal phase were discussed in the light of lattice dynamics calculations. A possible irreversible second phase transition to a highly disordered or amorphous state is detected in Raman scattering measurements above 21 GPa.Research supported by the Spanish government MINECO under Grant Nos. MAT and CSD2007-00045 and MAT2013-46649-C4-1/2/3-P. S.N.A. acknowledges the support provided by Universitat de Valencia during his visit there.Achary, SN.; Errandonea, D.; Santamaría-Pérez, D.; Gomis, O.; Patwe, SJ.; Manjón Herrera, FJ.; Rodríguez Hernández, P.... (2015). Experimental and theoretical investigations on structural and vibrational properties of melilite-type Sr2ZnGe2O7 at high pressure and delineation of a high pressure monoclinic phase. Inorganic Chemistry. 54(13):6594-6605. doi:10.1021/acs.inorgchem.5b00937S65946605541

Exploring the high-pressure behavior of the three known polymorphs of BiPO4: Discovery of a new polymorph

The following article appeared in Journal of Applied Physics and may be found at http://dx.doi.org/10.1063/1.4914407 . Authors own version of final article on e-print serversWe have studied the structural behavior of bismuth phosphate under compression. We performed x-ray powder diffraction measurements up to 31.5 GPa and ab initio calculations. Experiments were carried out on different polymorphs: trigonal (phase I) and monoclinic (phases II and III). Phases I and III, at low pressure (P < 0.2-0.8 GPa), transform into phase II, which has a monazite-type structure. At room temperature, this polymorph is stable up to 31.5 GPa. Calculations support these findings and predict the occurrence of an additional transition from the monoclinic monazite-type to a tetragonal scheelite-type structure (phase IV). This transition was experimentally found after the simultaneous application of pressure (28 GPa) and temperature (1500 K), suggesting that at room temperature the transition might by hindered by kinetic barriers. Calculations also predict an additional phase transition at 52 GPa, which exceeds the maximum pressure achieved in the experiments. This transition is from phase IV to an orthorhombic barite-type structure (phase V). We also studied the axial and bulk compressibility of BiPO4. Room-temperature pressure-volume equations of state are reported. BiPO4 was found to be more compressible than isomorphic rare-earth phosphates. The discovered phase IV was determined to be the less compressible polymorph of BiPO4. On the other hand, the theoretically predicted phase V has a bulk modulus comparable with that of monazite-type BiPO4. Finally, the isothermal compressibility tensor for the monazite-type structure is reported at 2.4 GPa showing that the direction of maximum compressibility is in the (0 1 0) plane at approximately 15 degrees (21 degrees) to the a axis for the case of our experimental (theoretical) study. (C) 2015 AIP Publishing LLC.Research supported by the Spanish government MINECO under Grant No: MAT2013-46649-C4-1/2/3-P and by Generalitat Valenciana under Grants Nos. GVA-ACOMP-2013-1012 and GVA-ACOMP/2014/243. B.G.-D. thanks the financial support from MEC through FPI program. Experiments were performed at MSPD beamline at ALBA Synchrotron Light Facility with the collaboration of ALBA staff.Errandonea, D.; Gomis, O.; Santamaría Pérez, D.; García-Domene, B.; Muñoz, A.; Rodríguez-Hernández, P.; Achary, SN.... (2015). Exploring the high-pressure behavior of the three known polymorphs of BiPO4: Discovery of a new polymorph. Journal of Applied Physics. 117:105902-1-105902-9. https://doi.org/10.1063/1.4914407S105902-1105902-911