Structural, Vibrational, and Elastic Properties of Yttrium Orthoaluminate Nanoperovskite at High Pressures

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, 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/page/policy/articlesonrequest/index.html."[EN] The structural and vibrational properties of nanocrystalline yttrium orthoaluminate perovskite (YAlO3) under compression have been experimentally studied. Experimental results have been compared to ab initio simulations of. bulk YAlO3, in the framework of the density functional theory. Furthermore, they have been complemented with an ab initio study of its elastic properties at different pressures. Calculated total and partial phonon density of states have allowed us to understand the contribution of the different atoms and structural units, YO12 dodecahedra and AlO6 octahedra, to the vibrational modes. The calculated infrared-active modes and their pressure dependence are also reported. Finally, the pressure dependences of the, elastic constants and the mechanical stability of the perovskite structure have been analyzed in detail, showing that this phase is mechanically stable until 92 GPa. In fact, experimental results up to 30 GPa show no evidence of any phase transition. A previously proposed possible phase transition in YAlO3 above 80 GPa is also discussed.This research was partially supported by MINECO (MAT2013-46649-C4-2/3/4-P, MAT2015-71070-REDC, and MAT2016-75586-C4-2/3/4-P) and by EU-FEDER funds. M.A.H.-R. thanks MINECO for an FPI grant (BES-2014-068666).Hernández-Rodríguez, M.; Monteseguro, V.; Lozano-Gorrín, A.; Manjón, F.; González-Platas, J.; Rodríguez-Hernández, P.; Muñoz, A.... (2017). Structural, Vibrational, and Elastic Properties of Yttrium Orthoaluminate Nanoperovskite at High Pressures. The Journal of Physical Chemistry C. 121(28):15353-15367. https://doi.org/10.1021/acs.jpcc.7b04245S15353153671212

Pressure-induced phase transition and band gap decrease in semiconducting β-Cu2V2O7

The understanding of the interplay between crystal structure and electronic structure in semiconductor materials is of great importance due to their potential technological applications. Pressure is an ideal external control parameter to tune the crystal structures of semiconductor materials in order to investigate their emergent piezo-electrical and optical properties. Accordingly, we investigate here the high-pressure behavior of the semiconducting antiferromagnetic material β-Cu2V2O7, finding it undergoes a pressure-induced phase transition to γ-Cu2V2O7 below 4000 atm. The pressure-induced structural and electronic evolutions are investigated by single-crystal X-ray diffraction, absorption spectroscopy and ab initio density functional theory calculations. β-Cu2V2O7 has previously been suggested as a promising photocatalyst for water splitting. Now, these new results suggest that β-Cu2V2O7 could also be of interest with regards to barocaloric effects, due to the low phase -transition pressure, in particular because it is a multiferroic material. Moreover, the phase transition involves an electronic band gap decrease of approximately 0.2 eV (from 1.93 to 1.75 eV) and a large structural volume collapse of approximately 7%.The authors acknowledge financial support from the Spanish Research Agency (AEI) and Spanish Ministry of Science and Investigation (MCIN) under projects PID2019106383GBC41/ C43/C44 (DOI: 10.13039/501100011033), and projects PGC2018-101464−B-I00 and PGC2018-097520-A-I00 (cofinanced by EU FEDER funds). The authors acknowledge financial support from the MALTA Consolider Team network, under project RED2018-102612-T. R.T. acknowledges funding from the Spanish Ministry of economy and competitiveness (MINECO) via the Juan de la Cierva Formación program (FJC2018-036185-I). J.G.P. thanks the Servicios Generales de Apoyo a la Investigación (SEGAI) at the University of La Laguna. A.L. and D.E. would like to thank the Generalitat Valenciana for the Ph.D. fellowship GRISOLIAP/2019/025, and the authors would also like to thank them for funding under the Grant Prometeo/2018/123 (EFIMAT). The authors also thank ALBA synchrotron light source for funded experiment under proposal numbers 2020074389 and 2020074398 at the MSPD-BL04 beamline

Lattice dynamics study of cubic Tb2O3

"This is the peer reviewed version of the following article: Ibáñez, Jordi, Oriol Blázquez, Sergi Hernández, Blas Garrido, Plácida Rodríguez-Hernández, Alfonso Muñoz, Matias Velázquez, Philippe Veber, and Francisco Javier Manjón. 2018. Lattice Dynamics Study of Cubic Tb 2 O 3. Journal of Raman Spectroscopy 49 (12). Wiley: 2021 27. doi:10.1002/jrs.5488, which has been published in final form at https://doi.org/10.1002/jrs.5488. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] We report a joint experimental and theoretical study of the lattice dynamics of cubic Tb2O3. Up to 16 optical Raman-active modes have been observed with polarized and unpolarized Raman scattering measurements on a high-quality Tb2O3 single crystal. The measured wavenumbers have been compared with those of other rare-earth (RE) and related sesquioxides with cubic (C-type or bixbyite) structure. First-principles calculations have allowed us to assign the symmetry of the experimentally observed Raman-active modes. Additional lattice-dynamical calculations on the related cubic RE sesquioxides Dy2O3, Gd2O3, Eu2O3, and Sm2O3 indicate that the phonon wavenumbers of the Raman-active modes in these compounds are monotonically reduced with increasing the lattice parameter along the Dy2O3-Tb2O3-Gd2O3-Eu2O3-Sm2O3 series, thus prompting for a revision of the experimental Raman spectra of some of these compounds (mainly Eu2O3 but also Gd2O3).This study was supported by the Spanish Ministerio de Economía y Competitividad under Projects MAT2015-71070-REDC, MAT2015-71035-R, MAT2016-75586-C4-2-P/3-P, and FIS2017-2017-83295-P.Ibanez, J.; Blazquez, O.; Hernandez, S.; Garrido, B.; Rodríguez-Hernández, P.; Munoz, A.; Velazquez, M.... (2018). Lattice dynamics study of cubic Tb2O3. Journal of Raman Spectroscopy. 49(12):2021-2027. https://doi.org/10.1002/jrs.5488S202120274912Pan, T.-M., Chen, F.-H., & Jung, J.-S. (2010). Structural and electrical characteristics of high-k Tb2O3 and Tb2TiO5 charge trapping layers for nonvolatile memory applications. Journal of Applied Physics, 108(7), 074501. doi:10.1063/1.3490179Kao, C. H., Liu, K. C., Lee, M. H., Cheng, S. N., Huang, C. H., & Lin, W. K. (2012). High dielectric constant terbium oxide (Tb2O3) dielectric deposited on strained-Si:C. Thin Solid Films, 520(8), 3402-3405. doi:10.1016/j.tsf.2011.10.173Gray, N. W., Prestgard, M. C., & Tiwari, A. (2014). Tb2O3 thin films: An alternative candidate for high-k dielectric applications. Applied Physics Letters, 105(22), 222903. doi:10.1063/1.4903072Geppert, I., Eizenberg, M., Bojarczuk, N. A., Edge, L. F., Copel, M., & Guha, S. (2010). Determination of band offsets, chemical bonding, and microstructure of the (TbxSc1−x)2O3/Si system. Journal of Applied Physics, 108(2), 024105. doi:10.1063/1.3427554Belaya, S. V., Bakovets, V. V., Boronin, A. I., Koshcheev, S. V., Lobzareva, M. N., Korolkov, I. V., & Stabnikov, P. A. (2014). Terbium oxide films grown by chemical vapor deposition from terbium(III) dipivaloylmethanate. Inorganic Materials, 50(4), 379-386. doi:10.1134/s0020168514040037Bakovets, V. V., Belaya, S. V., Lobzareva, M. N., & Maksimovskii, E. A. (2014). Kinetics of terbium oxide film growth from Tb(dpm)3 vapor. Inorganic Materials, 50(6), 576-581. doi:10.1134/s0020168514060016Veber, P., Velázquez, M., Gadret, G., Rytz, D., Peltz, M., & Decourt, R. (2015). Flux growth at 1230 °C of cubic Tb2O3single crystals and characterization of their optical and magnetic properties. CrystEngComm, 17(3), 492-497. doi:10.1039/c4ce02006eAbrashev, M. V., Todorov, N. D., & Geshev, J. (2014). Raman spectra of R2O3 (R—rare earth) sesquioxides with C-type bixbyite crystal structure: A comparative study. Journal of Applied Physics, 116(10), 103508. doi:10.1063/1.4894775Urban, M. W., & Cornilsen, B. C. (1987). Bonding anomalies in the rare earth sesquioxides. Journal of Physics and Chemistry of Solids, 48(5), 475-479. doi:10.1016/0022-3697(87)90108-9Hohenberg, P., & Kohn, W. (1964). Inhomogeneous Electron Gas. Physical Review, 136(3B), B864-B871. doi:10.1103/physrev.136.b864Kresse, G., & Furthmüller, J. (1996). Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 6(1), 15-50. doi:10.1016/0927-0256(96)00008-0Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., … Burke, K. (2008). Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Physical Review Letters, 100(13). doi:10.1103/physrevlett.100.136406Monkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Garcia-Domene, B., Ortiz, H. M., Gomis, O., Sans, J. A., Manjón, F. J., Muñoz, A., … Tyagi, A. K. (2012). High-pressure lattice dynamical study of bulk and nanocrystalline In2O3. Journal of Applied Physics, 112(12), 123511. doi:10.1063/1.4769747Gomis, O., Santamaría-Pérez, D., Ruiz-Fuertes, J., Sans, J. A., Vilaplana, R., Ortiz, H. M., … Mollar, M. (2014). High-pressure structural and elastic properties of Tl2O3. Journal of Applied Physics, 116(13), 133521. doi:10.1063/1.4897241K.Parlinski Phonon code seehttp://www.computingformaterials.com/.Todorov, N. D., Abrashev, M. V., Marinova, V., Kadiyski, M., Dimowa, L., & Faulques, E. (2013). Raman spectroscopy and lattice dynamical calculations of Sc2O3single crystals. Physical Review B, 87(10). doi:10.1103/physrevb.87.104301White, W. B., & Keramidas, V. G. (1972). Vibrational spectra of oxides with the C-type rare earth oxide structure. Spectrochimica Acta Part A: Molecular Spectroscopy, 28(3), 501-509. doi:10.1016/0584-8539(72)80237-xKranert, C., Schmidt-Grund, R., & Grundmann, M. (2014). Raman active phonon modes of cubic In2O3. physica status solidi (RRL) - Rapid Research Letters, 8(6), 554-559. doi:10.1002/pssr.201409004Ubaldini, A., & Carnasciali, M. M. (2008). Raman characterisation of powder of cubic RE2O3 (RE=Nd, Gd, Dy, Tm, and Lu), Sc2O3 and Y2O3. Journal of Alloys and Compounds, 454(1-2), 374-378. doi:10.1016/j.jallcom.2006.12.067Mochizuki, S., Fujishiro, F., & Ishiwata, K. (2005). Photo-induced valence-number changes and defects in Eu2O3fine particle films. Journal of Physics: Conference Series, 21, 189-194. doi:10.1088/1742-6596/21/1/03

Experimental and Theoretical Studies on alfa-In2Se3 at High Pressure

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://doi.org/10.1021/acs.inorgchem.8b00778[EN] alpha(R)-In2Se3 has been experimentally and theoretically studied under compression at room temperature by means of X-ray diffraction and Raman scattering measurements as well as by ab initio total-energy and lattice-dynamics calculations. Our study has confirmed the alpha (R3m) -> beta' (C2/m) ? beta (R (3) over barm) sequence of pressure-induced phase transitions and has allowed us to understand the mechanism of the monoclinic C2/m to rhombohedral R (3) over barm phase transition. The monoclinic C2/m phase enhances its symmetry gradually until a complete transformation to the rhombohedral R (3) over barm structure is attained above 10-12 GPa. The second-order character of this transition is the reason for the discordance in previous measurements. The comparison of Raman measurements and lattice-dynamics calculations has allowed us to tentatively assign most of the Raman-active modes of the three phases. The comparison of experimental results and simulations has helped to distinguish between the different phases of In2Se3 and resolve current controversies.The authors acknowledge financial support from Spanish government MINECO, the Spanish Agencia Estatal de Investigacion (AEI), and Fondo Europeo de Desarrollo Regional (FEDER) under Grants No. MAT2016-75586-C4-1/2/3-P and MAT2015-71070-REDC.Vilaplana Cerda, RI.; Gallego-Parra, S.; Jorge-Montero, A.; Rodríguez-Hernández, P.; Muñoz, A.; Errandonea, D.; Segura, A.... (2018). Experimental and Theoretical Studies on alfa-In2Se3 at High Pressure. Inorganic Chemistry. 57:8241-8252. https://doi.org/10.1021/acs.inorgchem.8b00778S824182525

Study of the orpiment and anorpiment phases of As2S3 under pressure

[EN] In this work we study the pressure behaviour of the orpiment (monoclinic) and anorpiment (triclinic) layered structures of As2S3 by means of ab initio calculations performed within the density functional theory, as part of an ongoing theoretical and experimental joint effort to provide a comprehensive picture of the bonding of this interesting material and the evolution of its structural, electronic, and vibrational properties under pressure.The authors acknowledge the financial support from the Ministerio de Economia y Competitividad (MINECO) of Spain through Projects No. MAT2013-46649-C04-02-P and MAT2013-46649-C04-03-P. Computer time in the MALTA computer cluster at the University of Oviedo, Spain, is also gratefully acknowledged (MINECO Project No. CSD2007-00045).Randescu, S.; Mújica, A.; Rodríguez-Hernández, P.; Muñoz, A.; Ibañez, J.; Sans-Tresserras, JÁ.; Cuenca Gotor, VP.... (2017). Study of the orpiment and anorpiment phases of As2S3 under pressure. Journal of Physics: Conference Series. 950:042018-042018. https://doi.org/10.1088/1742-6596/950/4/042018S042018042018950Brazhkin, V. V., Katayama, Y., Kondrin, M. V., Lyapin, A. G., & Saitoh, H. (2010). Structural transformation yielding an unusual metallic state in liquidAs2S3under high pressure. Physical Review B, 82(14). doi:10.1103/physrevb.82.140202Gibbs, G. V., Wallace, A. F., Zallen, R., Downs, R. T., Ross, N. L., Cox, D. F., & Rosso, K. M. (2010). Bond Paths and van der Waals Interactions in Orpiment, As2S3. The Journal of Physical Chemistry A, 114(23), 6550-6557. doi:10.1021/jp102391aKampf, A. R., Downs, R. T., Housley, R. M., Jenkins, R. A., & Hyršl, J. (2011). Anorpiment, As2S3, the triclinic dimorph of orpiment. Mineralogical Magazine, 75(6), 2857-2867. doi:10.1180/minmag.2011.075.6.2857Bolotina, N. B., Brazhkin, V. V., Dyuzheva, T. I., Katayama, Y., Kulikova, L. F., Lityagina, L. V., & Nikolaev, N. A. (2014). High-pressure polymorphism of As2S3 and new AsS2 modification with layered structure. JETP Letters, 98(9), 539-543. doi:10.1134/s0021364013220025Bolotina, N. B., Brazhkin, V. V., Dyuzheva, T. I., Lityagina, L. M., Kulikova, L. F., Nikolaev, N. A., & Verin, I. A. (2013). Crystal structure of new AsS2 compound. Crystallography Reports, 58(1), 61-64. doi:10.1134/s1063774513010069Kresse, G., & Hafner, J. (1993). Ab initiomolecular dynamics for liquid metals. Physical Review B, 47(1), 558-561. doi:10.1103/physrevb.47.558Kresse, G., & Furthmüller, J. (1996). Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 6(1), 15-50. doi:10.1016/0927-0256(96)00008-0Kresse, 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.54.11169Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., … Burke, K. (2008). Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Physical Review Letters, 100(13). doi:10.1103/physrevlett.100.136406Kresse, 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.50.17953Monkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Grimme, S. (2006). Semiempirical GGA-type density functional constructed with a long-range dispersion correction. Journal of Computational Chemistry, 27(15), 1787-1799. doi:10.1002/jcc.20495Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics, 132(15), 154104. doi:10.1063/1.3382344Birch, F. (1947). Finite Elastic Strain of Cubic Crystals. Physical Review, 71(11), 809-824. doi:10.1103/physrev.71.809Mujica, 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.75.863Alfè, D. (2009). PHON: A program to calculate phonons using the small displacement method. Computer Physics Communications, 180(12), 2622-2633. doi:10.1016/j.cpc.2009.03.01

Pressure effects on the vibrational properties of alpha-Bi2O3: an experimental and theoretical study

We report an experimental and theoretical high-pressure study of the vibrational properties of synthetic monoclinic bismuth oxide (alpha-Bi2O3), also known as mineral bismite. The comparison of Raman scattering measurements and theoretical lattice-dynamics ab initio calculations is key to understanding the complex vibrational properties of bismite. On one hand, calculations help in the symmetry assignment of phonons and to discover the phonon interactions taking place in this low-symmetry compound, which shows considerable phonon anticrossings; and, on the other hand, measurements help to validate the accuracy of first-principles calculations relating to this compound. We have also studied the pressure-induced amorphization (PIA) of synthetic bismite occurring around 20 GPa and showed that it is reversible below 25 GPa. Furthermore, a partial temperature-induced recrystallization (TIR) of the amorphous sample can be observed above 20 GPa upon heating to 200 C, thus evidencing that PIA at room temperature occurs because of the inability of the a phase to undergo a phase transition to a high-pressure phase. Raman scattering measurements of the TIR sample at room temperature during pressure release have been performed. The interpretation of these results in the light of ab initio calculations of the candidate phases at high pressures has allowed us to tentatively attribute the TIR phase to the recently found high-pressure hexagonal HPC phase and to discuss its lattice dynamics.This work has been supported by Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under project 201050/2012-9, by Ministerio de Ciencia e Innovacion of Spain (MICINN) under the National Program of Materials (MAT2010-21270-C04-03/04) and the Consolider-Ingenio 2010 Program (MALTA CSD2007-0045) and by Generalitat Valenciana through projects GVA-ACOMP-2013-012 and Prometeo 2009/053.Pereira, ALJ.; Gomis, O.; Sans, JA.; Pellicer-Porres, J.; Manjón Herrera, FJ.; Beltran, A.; Rodríguez-Hernández, P.... (2014). Pressure effects on the vibrational properties of alpha-Bi2O3: an experimental and theoretical study. Journal of Physics: Condensed Matter. 26(22):225401-1-225401-15. https://doi.org/10.1088/0953-8984/26/22/225401S225401-1225401-15262

High-Pressure Properties of Wolframite-Type ScNbO4

In this work, we used Raman spectroscopic and optical absorption measurements and first-principles calculations to unravel the properties of wolframite-type ScNbO4 at ambient pressure and under high pressure. We found that monoclinic wolframite-type ScNbO4 is less compressible than most wolframites and that under high pressure it undergoes two phase transitions at ∼5 and ∼11 GPa, respectively. The first transition induces a 9% collapse of volume and a 1.5 eV decrease of the band gap energy, changing the direct band gap to an indirect one. According to calculations, pressure induces symmetry changes (P2/c–Pnna–P2/c). The structural sequence is validated by the agreement between phonon calculations and Raman experiments and between band structure calculations and optical absorption experiments. We also obtained the pressure dependence of Raman modes and proposed a mode assignment based upon calculations. They also provided information on infrared modes and elastic constants. Finally, noncovalent and charge analyses were employed to analyze the bonding evolution of ScNbO4 under pressure. They show that the bonding nature of ScNbO4 does not change significantly under pressure. In particular, the ionicity of the wolframite phase is 61% and changes to 63.5% at the phase transition taking place at ∼5 GPa

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