John Peter Brodholt

• Backhouse, Nicholas; Thomson, Andrew; Brodholt, John Peter; Hrubiak, Rostislav; Crichton, Wilson & Hao, Ming [Show all 9 contributors for this article] (2026). Seismic Velocity of Chlorite Under High Pressure and Temperature and Implications for the Lesser Antilles Subduction Zone. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 131(9), p. 1–13. doi: 10.1029/2025jb032997. Full text in Research Archive Show summary

  Abstract Chlorite is thought to be one of the major water‐carrying phases in subduction zones, both within the slab and in the mantle wedge. Its presence has previously been linked to common seismological observations at subduction zones, including P and S wave anisotropy as well as high V P / V S ratios (>1.8) in the mantle wedge. However, at present, there are very few high pressure and temperature measurements of the seismic velocity of chlorite at subduction zone conditions, hampering accurate seismological interpretations. This study presents seismic velocities and PVT equation of state measurements of two natural monomineralic chlorite schists, at conditions extending up to ∼5 GPa and 773K. One major finding is the anomalously high V P / V S ratio of these samples, which increase >3 at 5 GPa and 773 K. This result suggests that only a small amount of chlorite (<10%) is required in mantle peridotite assemblages to reproduce the observed V P / V S anomalies >1.8, such as those in the Lesser Antilles subduction zone, and that regions with high V P / V S are not necessarily diagnostic of a free fluid.

• Yang, Hua; Wan, Lei; Li, Yunguo; Vočadlo, Lidunka & Brodholt, John (2026). Molecular‐Dynamics Study of the Crystal Structure of Iron Under the Earth's Inner Core Conditions. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 131(1). doi: 10.1029/2025jb032139. Full text in Research Archive Show summary

  Abstract The crystal structure of Earth's solid inner core is fundamental to understanding the chemical composition and dynamical evolution of the core. However, despite extensive research, the structure still remains controversial with competing hypotheses regarding the stability of various Fe phases (e.g., bcc, fcc, and hcp). In this paper, we review the studies on the crystal structure of Fe under inner core conditions, and find, in line with previous work, that the main challenges come from the small energy differences between these structures. This has led to a variety of different conclusions across varying theoretical methods and precision, including ab initio, force field and machine learning methods. To address this problem, we employ a Bain path thermodynamic integration approach to reach consistent conclusions among different methods; we find that bcc Fe is mechanically stable but thermodynamically less stable under inner core conditions. Using the energetics from the Bain path method as a benchmark, we establish the requirements for converging free energy calculations through a two‐phase thermodynamic modeling approach. These calculations confirm that the hcp phase is the most stable, exhibiting the highest melting temperature regardless of the method used. This unified conclusion on the hcp phase as the stable crystal structure provides a robust foundation for future studies on Earth's core.

• Dou, Peixue; Brodholt, John Peter; Vočadlo, Lidunka; Li, Yunguo & Ni, Huaiwei (2026). Point defects as a control on the viscosity jump in the lower mantle. Earth and Planetary Science Letters. ISSN 0012-821X. 684. doi: 10.1016/j.epsl.2026.120008. Full text in Research Archive
• Thomson, A. R.; Crichton, W. A.; Siersch, N. C.; Ezad, I. S.; Dobson, D. P. & Brodholt, J. P. (2025). Experimental observations of CaSiO3-CaTiO3 perovskites: implications for Ca-rich inclusions observed in sub-lithospheric diamonds. Physics and chemistry of minerals. ISSN 0342-1791. 52(2). doi: 10.1007/s00269-025-01321-z. Full text in Research Archive Show summary

  Abstract Calcium perovskite is a major component of deep mantle phase assemblages and has been frequently identified, in retrograde form, as polyphase mineral inclusions within sub-lithospheric diamonds. Here experimental observations of synthetic samples demonstrate various properties of calcium perovskite minerals which have relevance for the interpretation of diamond-hosted inclusions. Ambient pressure diffraction and spectroscopy confirm the linear dependence of crystallographic unit cell volume and Raman peak shifts across the entire CaSiO 3 -CaTiO 3 binary join. These systematics will allow verification of perovskite structure and constraint of inclusion composition, without destructive analyses, in future studies. Additionally, high pressure observations confirm that calcium perovskite minerals ≳ 80 mol.% CaSiO 3 undergo spontaneous amorphization during decompression at room temperature, meaning they are unrecoverable. Finally, the presence of water appears to expand the calcium perovskite stability field to lower pressure conditions, implying at least some appreciable water-solubility in these minerals.

• Huang, Rong; Thomson, Andrew R.; Brodholt, John Peter; Crichton, Wilson A.; Rosenthal, Anja & Druzhbin, Dmitrii [Show all 11 contributors for this article] (2025). Sound velocity measurements of γ-(Mg0.91Fe0.09)2SiO4 show that the ringwoodite to bridgmanite and ferropericlase phase transformation does not produce the seismically observed 660 km discontinuity. Earth and Planetary Science Letters. ISSN 0012-821X. 663, p. 119416–119416. doi: 10.1016/j.epsl.2025.119416. Full text in Research Archive
• Driel, Jac van; Vočadlo, Lidunka & Brodholt, John Peter (2025). Thermodynamics of Fe-S-O-C-H liquids: Implications for the Martian core. Earth and Planetary Science Letters. ISSN 0012-821X. 668. doi: 10.1016/j.epsl.2025.119540. Full text in Research Archive Show summary

  We present a comprehensive investigation into the composition of the Martian core. We use new density functional theory (DFT) calculations, which consider in detail the magnetic properties of the Fe alloys, essential for obtaining the correct density and velocities. We then fit our results to a new Gaussian Process Regression (GPR) equation of state (EOS). Using this GPR-EOS we search for all compositions of the Martian core in the system Fe-S-O-C-H that match both the density and compressional wave speeds of a liquid Martian core throughout its entire depth range. We consider different models for the interior of Mars – in particular, those with and without a deep melt layer at the base of the Martian mantle (Irving et al., 2023; Samuel et al., 2023; Khan et al., 2023). The existence of a deep melt layer is important as it revises previous estimates for the core's size and density. We consider a range of core-mantle boundary temperatures from 1900 K to 2850 K, although we find that temperature has a relatively small effect on the possible compositions. As with previous studies, and also for the Earth, we find many different compositions that are able to match the geophysical observations of Mars' core density (ρ) and velocity ( ), regardless of which set of geophysical observations are used. All models require very high concentrations of light-elements of ≈ 50 mol% in line with previous work. The compositional variation can be reduced considerably by considering cosmochemical constraints on the maximum amount of sulphur, together with geochemical constraints on the partitioning. In this case, all solutions require very high hydrogen content of at least 0.5 wt% (27 mol%) and practically no oxygen.

• Hatalova, Petra; Brodholt, John Peter; Brasser, Ramon; Shan, Yutong & Werner, Stephanie C. (2025). The compositional diversity of rocky exoplanets around K-dwarf stars. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 694. doi: 10.1051/0004-6361/202451070. Full text in Research Archive Show summary

  Context. The mass-radius distribution of currently known exoplanets suggests a fascinating variety in terms of their chemical compositions. Still, the interior structures and compositions of rocky exoplanets are essentially inaccessible to observations. Here, we present a model that combines planet formation simulations with equilibrium condensation models to estimate the interior composition and structure of exoplanets around K-dwarf stars. Aims. In a previous study, we reproduced the observed population of close-in super-Earths around K-dwarf stars with suitable initial conditions. However, the masses and radii of these simulated planets are not self-consistent, since the radius information is postprocessed based on an assumed constant average density (3 g cm−3). In this work, we have incorporated compositions into the N-body simulations using the chemistry of the protoplanetary disk from equilibrium condensation sequences, together with thermodynamics of the various mineral phases. This has allowed us to develop models of likely interior structures, bulk densities, and, thus, radii for rocky exoplanets. Methods. We selected the outcomes of ten N-body simulations around a 0.8 M⊙ star that best reproduced the observed population. We employed stellar abundances from six K-dwarf stars with a range of metallicities. Based on the condensation sequence and the temperature-pressure profile of a disk, we assigned bulk elemental compositions to planetesimals and then tracked materials accreted onto planets during their formation. Results. We have obtained a set of planets with more realistic radii determinations than those purely based on one preset density for all bodies. We formed various types of planets: i) Ca- and Al-rich(er), ii) Mg-depleted, iii) fully oxidized core-less planets, iv) planets similar to Earth or Mars in composition and core size, and v) planets with different core mass fractions (from significantly smaller than the Martian core to significantly larger than the Earth’s core); however, we do not have Mercury-like planet with a huge core.

• Zhang, Chi; Yang, Jin-Yuan; Sun, Tao; Zhang, Huai & Brodholt, John Peter (2025). Strong precursor softening in cubic CaSiO<inf>3</inf> perovskite. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 122(5). doi: 10.1073/pnas.2410910122. Full text in Research Archive Show summary

  CaSiO3 perovskite (CaPv) is the last major mineral in the Earth’s lower mantle whose elasticity remains largely unresolved. Here, we investigate the elasticity of CaPv using ab initio machine-learning force fields (MLFF). At room temperature, the elasticity of tetragonal CaPv determined by MLFF molecular dynamics (MD) agrees well with experimental measurements after considering temperature induced variations in the hydrostatic structure, proving the effectiveness of the method. We use the MLFF MD in the NPT ensemble to establish the tetragonal–cubic phase boundary and confirm that in the lower mantle CaPv is in the cubic phase. The elasticity of cubic CaPv shows distinct temperature dependence at different ranges: it is linear at high temperatures, whereas it exhibits anomalous precursor softening near the tetragonal–cubic phase boundary. The temperature interval of precursor softening widens as the pressure increases and overlaps with the temperature profile of subducted cold slabs near the core–mantle boundary. While cubic CaPv is seismically invisible along the average mantle geotherm, it may induce low-velocity zones with negative temperature anomaly, leading to the view that the large low shear velocity provinces (LLSVPs) may be caused by subducted oceanic crust rich in CaPv with temperature lower than ambient mantle. A cool, rigid LLSVP may help explain the preferential formation of mantle plumes at its margins, as well as its weaker seismic anisotropy.

• Luo, Haiyang; Vočadlo, Lidunka & Brodholt, John Peter (2024). Iron isotope fractionation between metal and silicate during core-mantle differentiation in rocky bodies. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 379, p. 184–192. doi: 10.1016/j.gca.2024.07.002. Full text in Research Archive
• Wang, Wenzhong; Walter, Michael J.; Brodholt, John Peter & Huang, Shichun (2024). Early planetesimal differentiation and late accretion shaped Earth’s nitrogen budget. Nature Communications. 15. doi: 10.1038/s41467-024-48500-0. Full text in Research Archive Show summary

  The relative roles of protoplanetary differentiation versus late accretion in establishing Earth’s life-essential volatile element inventory are being hotly debated. To address this issue, we employ first-principles calculations to investigate nitrogen (N) isotope fractionation during Earth’s accretion and differentiation. We find that segregation of an iron core would enrich heavy N isotopes in the residual silicate, while evaporation within a H2-dominated nebular gas produces an enrichment of light N isotope in the planetesimals. The combined effect of early planetesimal evaporation followed by core formation enriches the bulk silicate Earth in light N isotopes. If Earth is comprised primarily of enstatite-chondrite-like material, as indicated by other isotope systems, then late accretion of carbonaceous-chondrite-like material must contribute ~ 30–100% of the N budget in present-day bulk silicate Earth. However, mass balance using N isotope constraints shows that the late veneer contributes only a limited amount of other volatile elements (e.g., H, S, and C) to Earth.

• Chotalia, K.; Brodholt, John Peter & Lithgow-Bertelloni, C. (2023). Surface exposure constraints on the mantle water budget. Geology. ISSN 0091-7613. 51(9), p. 890–894. doi: 10.1130/G51221.1. Full text in Research Archive
• Wang, Wenzhong; Walter, Michael J.; Brodholt, John Peter; Huang, Shichun & Petaev, Michail I. (2023). Chalcogen isotopes reveal limited volatile contribution from late veneer to Earth. Science Advances. 9(49). doi: 10.1126/sciadv.adh0670. Full text in Research Archive Show summary

  The origin of Earth’s volatile elements is highly debated. Comparing the chalcogen isotope ratios in the bulk silicate Earth (BSE) to those of its possible building blocks, chondritic meteorites, allows constraints on the origin of Earth’s volatiles; however, these comparisons are complicated by potential isotopic fractionation during protoplanetary differentiation, which largely remains poorly understood. Using first-principles calculations, we find that core-mantle differentiation does not notably fractionate selenium and tellurium isotopes, while equilibrium evaporation from early planetesimals would enrich selenium and tellurium in heavy isotopes in the BSE. The sulfur, selenium, and tellurium isotopic signatures of the BSE reveal that protoplanetary differentiation plays a key role in establishing most of Earth’s volatile elements, and a late veneer does not substantially contribute to the BSE’s volatile inventory.

• Huang, D; Murakami, M.; Brodholt, John Peter; McCammon, C. & Petitgirard, S (2022). Structural evolution in a pyrolitic magma ocean under mantle conditions. Earth and Planetary Science Letters. ISSN 0012-821X. 584. doi: 10.1016/j.epsl.2022.117473. Full text in Research Archive
• Li, Yunguo; Vočadlo, Lidunka & Brodholt, John Peter (2022). ElasT: A toolkit for thermoelastic calculations. Computer Physics Communications. ISSN 0010-4655. 273. doi: 10.1016/j.cpc.2021.108280. Full text in Research Archive
• Huang, D; Brodholt, John Peter; Sossi, P; Li, Y & Murakami, M. (2022). Nitrogen speciation in silicate melts at mantle conditions from ab initio simulations. Geophysical Research Letters. ISSN 0094-8276. 49(7). doi: 10.1029/2021GL095546. Full text in Research Archive
• Ezad, IS; Einsle, JF; Dobson, DP; Hunt, SA; Thomson, AR & Brodholt, John Peter (2022). Improving grain size analysis using computer vision techniques and implications for grain growth kinetics. American Mineralogist. ISSN 0003-004X. 107(2), p. 262–273. doi: 10.2138/am-2021-7797. Full text in Research Archive
• Drewitt, JWE; Walter, MJ; Brodholt, John Peter; Muir, JMR & Lord, Oliver T. (2022). Hydrous silicate melts and the deep mantle H2O cycle. Earth and Planetary Science Letters. ISSN 0012-821X. 581. doi: 10.1016/j.epsl.2022.117408. Full text in Research Archive
• Ezad, IS; Dobson, DP; Thomson, AR; Jennings, ES; Hunt, SA & Brodholt, John Peter (2022). Kelyphite textures experimentally reproduced through garnet breakdown in the presence of a melt phase. Journal of Petrology. ISSN 0022-3530. 63(11). doi: 10.1093/petrology/egac110. Full text in Research Archive
• Li, Yunguo; Guo, Xuan; Vočadlo, Lidunka; Brodholt, John Peter & Ni, Huaiwei (2022). The effect of water on the outer core transport properties. Physics of the Earth and Planetary Interiors. ISSN 0031-9201. 329-330. doi: 10.1016/j.pepi.2022.106907. Full text in Research Archive
• Li, Yunguo; Vočadlo, Lidunka; Ballentine, Chris & Brodholt, John Peter (2022). Primitive noble gases sampled from ocean island basalts cannot be from the Earth’s core. Nature Communications. 13. doi: 10.1038/s41467-022-31588-7. Full text in Research Archive Show summary

  Abstract Noble gas isotopes in plumes require a source of primitive volatiles largely isolated in the Earth for 4.5 Gyrs. Among the proposed reservoirs, the core is gaining interest in the absence of robust geochemical and geophysical evidence for a mantle source. This is supported by partitioning data showing that sufficient He and Ne could have been incorporated into the core to source plumes today. Here we perform ab initio calculations on the partitioning of He, Ne, Ar, Kr and Xe between liquid iron and silicate melt under core forming conditions. For He our results are consistent with previous studies allowing for substantial amounts of He in the core. In contrast, the partition coefficient for Ne is three orders of magnitude lower than He. This very low partition coefficient would result in a 3 He/ 22 Ne ratio of ~10 3 in the core, far higher than observed in ocean island basalts (OIBs). We conclude that the core is not the source of noble gases in OIBs.

• Wang, Wenzhong; Li, Chun-Hui; Brodholt, John Peter; Huang, Shichun; Walter, Michael J. & Li, Min [Show all 9 contributors for this article] (2021). Sulfur isotopic signature of Earth established by planetesimal volatile evaporation. Nature Geoscience. ISSN 1752-0894. 14, p. 806–811. doi: 10.1038/s41561-021-00838-6. Full text in Research Archive
• Wang, W; Li, Yunguo; Brodholt, John Peter; Vocadlo, Lidunka; Walter, Michael J. & Wu, Zhongqing (2021). Strong shear softening induced by superionic hydrogen in Earth's inner core. Earth and Planetary Science Letters. ISSN 0012-821X. 568. doi: 10.1016/j.epsl.2021.117014. Full text in Research Archive
• Li, Y; Vocadlo, Lidunka; Edgington, A & Brodholt, John Peter (2021). Equation of state for CO and CO2 fluids and their application on decarbonation reactions at high pressure and temperature. Chemical Geology. ISSN 0009-2541. 559. doi: 10.1016/j.chemgeo.2020.119918. Full text in Research Archive
• Wang, Wenzhong; Zhang, Han; Brodholt, John Peter & Wu, Zhongqing (2021). Elasticity of hydrous ringwoodite at mantle conditions: Implication for water distribution in the lowermost mantle transition zone. Earth and Planetary Science Letters. ISSN 0012-821X. 554. doi: 10.1016/j.epsl.2020.116626. Full text in Research Archive
• Thomson, Andrew R.; Piltz, Ross O.; Crichton, Wilson A.; Cerantola, Valerio; Ezad, Isra S. & Dobson, David P. [Show all 8 contributors for this article] (2021). Incorporation of tetrahedral ferric iron into hydrous ringwoodite. American Mineralogist. ISSN 0003-004X. 106(6), p. 900–908. doi: 10.2138/am-2021-7539. Full text in Research Archive
• Das, Pratik Kumar; Mohn, Chris Erik; Brodholt, John Peter & Trønnes, Reidar G (2020). High pressure silica phase transitions: Implications for deep mantle dynamics and silica crystallization in the protocore. American Mineralogist. ISSN 0003-004X. 105, p. 1014–1020. doi: 10.2138/am-2020-7299. Full text in Research Archive
• Pamato, MG; Li, Y; Antonangeli, D; Miozzi, F; Morard, G & Wood, IG [Show all 9 contributors for this article] (2020). Equation of state of hcp Fe‐C‐Si alloys and the effect of C incorporation mechanism on the density of hcp Fe alloys at 300 K. Journal of Geophysical Research (JGR). ISSN 0148-0227. 125(12). doi: 10.1029/2020JB020159. Full text in Research Archive
• Wang, Kai; Lu, Xiancai & Brodholt, John Peter (2020). Diffusion of noble gases in subduction zone hydrous minerals. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 291, p. 50–61. doi: 10.1016/j.gca.2020.07.015. Full text in Research Archive
• Muir, JMR & Brodholt, John Peter (2020). Ferric iron in bridgmanite and implications for ULVZs. Physics of the Earth and Planetary Interiors. ISSN 0031-9201. 306. doi: 10.1016/j.pepi.2020.106505. Full text in Research Archive
• Li, Y; Vocadlo, Lidunka; Sun, T & Brodholt, John Peter (2020). The Earth’s core as a reservoir of water. Nature Geoscience. ISSN 1752-0894. 13, p. 453–458. doi: 10.1038/s41561-020-0578-1. Full text in Research Archive
• Chotalia, Kiran; Cagney, Neil; Lithgow-Bertelloni, Carolina & Brodholt, John Peter (2020). The coupled effects of mantle mixing and a water-dependent viscosity on the surface ocean. Earth and Planetary Science Letters. ISSN 0012-821X. 530. doi: 10.1016/j.epsl.2019.115881. Full text in Research Archive
• Driel, J van; Schusteritsch, G; Brodholt, John Peter; Dobson, DP & Pickard, CJ (2020). The discontinuous effect of pressure on twin boundary strength in MgO. Physics and chemistry of minerals. ISSN 0342-1791. 47. doi: 10.1007/s00269-019-01079-1. Full text in Research Archive
• Thomson, AR; Crichton, WA; Brodholt, John Peter; Wood, IG; Siersch, NC & Muir, JMR [Show all 8 contributors for this article] (2019). Seismic velocities of CaSiO3 perovskite can explain LLVPs in Earth’s lower mantle. Nature. ISSN 0028-0836. 572, p. 643–647. doi: 10.1038/s41586-019-1483-x. Full text in Research Archive
• Huang, D; Badro, J; Brodholt, John Peter & Li, Y (2019). Ab initio molecular dynamics investigation of molten Fe-Si-O in Earth's core. Geophysical Research Letters. ISSN 0094-8276. 46(12), p. 6397–6405. doi: 10.1029/2019GL082722. Full text in Research Archive
• Dobson, David P.; Lindsay-Scott, Alexander; Hunt, Simon A; Bailey, Edward; Wood, Ian G. & Brodholt, John Peter [Show all 8 contributors for this article] (2019). Anisotropic diffusion creep in postperovskite provides a new model for deformation at the core−mantle boundary. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 116(52), p. 26389–26393. doi: 10.1073/pnas.1914826116. Full text in Research Archive
• Li, Yunguo; Vocadlo, Lidunka; Alfè, Dario & Brodholt, John Peter (2019). Carbon partitioning between the Earth's inner and outer core. Journal of Geophysical Research (JGR). ISSN 0148-0227. 124(12), p. 12812–12824. doi: 10.1029/2019JB018789. Full text in Research Archive
• Sun, Tao; Brodholt, John Peter; Li, Yunguo & Vocadlo, Lidunka (2018). Melting properties from ab initio free energy calculations: Iron at the Earth's inner-core boundary. Physical review B (PRB). ISSN 2469-9950. 98(22). doi: 10.1103/PhysRevB.98.224301. Full text in Research Archive
• Li, Yunguo; Vocadlo, Lidunka & Brodholt, John Peter (2018). The elastic properties of hcp-Fe alloys under the conditions of the Earth's inner core. Earth and Planetary Science Letters. ISSN 0012-821X. 493, p. 118–127. doi: 10.1016/j.epsl.2018.04.013. Full text in Research Archive
• Zhang, Zhigang; Mao, Zhu; Liu, Xi; Zhang, Yigang & Brodholt, John Peter (2018). Stability and Reactions of CaCO3 Polymorphs in the Earth's Deep Mantle. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 123(8), p. 6491–6500. doi: 10.1029/2018JB015654. Full text in Research Archive

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• Das, Pratik Kumar; Mohn, Chris Erik; Trønnes, Reidar G & Brodholt, John Peter (2019). Silica phase transitions at lowermost mantle and core conditions. Goldschmidt Conference Abstracts. Full text in Research Archive
• Driel, J van; Brodholt, John Peter & Dobson, DP (2019). Constraining grain boundary diffusion within the Earth's lower mantle. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr.. Full text in Research Archive
• Drewitt, JWE; Walter, MJ; Brodholt, John Peter & Muir, JMR (2019). Density of hydrous silicate melts in the transition zone. AGU Fall Meeting Abstr.. Full text in Research Archive

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