Katherine Crispin | Pennsylvania State University (original) (raw)

Papers by Katherine Crispin

Fe cation diffusion plays a fundamental role for many processes in Earth's mantle involving c... more Fe cation diffusion plays a fundamental role for many processes in Earth's mantle involving chemical, isotopic and advective mass transfer, and can potentially control homogenization of mantle materials and equilibration of elements between the core and mantle. Present data on Fe transport in Fp is limited to pressures below the top of the lower mantle and therefore must be extrapolated to model lower mantle conditions. However, extrapolation of Fe diffusion properties from measurements under 35 GPa to lower mantle pressures is quite uncertain due to uncertainty in the Fe activation volume and its unknown pressure dependence. In particular, the existing diffusion data includes no information on the effect of the recently discovered Fe spin transition. In the present study we combine first principles methods with statistical diffusion models to compute the Fe2+ diffusivity in dilute Fe ferropericlase at lower mantle pressures and temperatures. Diffusivities are determined for pur...

Trivalent impurities govern cation vacancy concentrations in most minerals, and thus play a centr... more Trivalent impurities govern cation vacancy concentrations in most minerals, and thus play a central role in solid-state diffusion in the Earth. Periclase is the second most abundant mineral in the lower mantle and is a key to understanding creep and chemical exchange mechanisms. Although periclase is among the simplest of minerals, diffusion of trivalent cations is a complex process. Trivalent cations tend to bind to oppositely charged cation vacancies to form pairs, and in some cases higher-order complexes. Impurity-vacancy pairs are extremely mobile species; the continual presence of a vacancy adjacent to the trivalent impurity allows it to move through the lattice much more rapidly than it would in the absence of binding. We have performed experiments on diffusion of Ga, Sc, Y and Cr in periclase, and developed a theoretical approach to extract the binding energy and impurity-vacancy pair diffusivity from the experimental diffusion profiles. Experiments were performed in an open ...

Geochmica et Cosmochimica Acta

Recent experimental results on diffusion of Ga3+ and Cr3+ in periclase indicate that the electron... more Recent experimental results on diffusion of Ga3+ and Cr3+ in periclase indicate that the electronic structure of transition metal cations has a strong influence on their diffusivity (Crispin and Van Orman, 2010). Transition metal cations with partially filled d-orbitals are stabilized on octahedral sites by the crystal field effect, which increases the energy barrier for the migration of cations to adjacent vacancies. A previous study of divalent transition metals (Wuensch and Vasilos, 1962) found that the diffusivity increased in the order Ni

Diffusion in minerals is the rate-limiting step in many mass transport processes that are fundame... more Diffusion in minerals is the rate-limiting step in many mass transport processes that are fundamental to geochemistry and geophysics. Thus, there has been a long-standing interest in finding theoretical or empirical relationships that relate the diffusion coefficient in a mineral to well-known ionic properties such as radius and charge. In many silicate minerals the diffusion coefficient is negatively correlated with ionic charge. In periclase, and some other minerals with a strong component of ionic bonding, highly charged cations diffuse rapidly due to their association with cation vacancies. Experiments on Al3+ diffusion in MgO have been performed over a wide range of pressure (1 atm to 25 GPa) and temperature (1573 to 2273 K), and the association energy and Al- vacancy pair diffusivity inferred from each by applying a simple defect interaction model to the diffusion profiles. The binding energy for all but one experiment is in the range 0.45-0.62 eV, and shows no clear dependenc...

Periclase is the second most abundant mineral in Earth's lower mantle and is a key to underst... more Periclase is the second most abundant mineral in Earth's lower mantle and is a key to understanding chemical exchange mechanisms and diffusive length scales at the core-mantle boundary. The crystal field effect has long been known to influence the partitioning of first-row transition metals in minerals, but its influence on diffusion has not previously been considered. Transition metal cations with partially filled d-orbitals are stabilized on octahedral sites by the crystal field effect; this crystal field stabilization may increase the energy barrier for the migration of cations to adjacent vacancies. To investigate the influence of the crystal field effect on diffusion in periclase, ideally one would hold all variables constant except for electronic structure. Two cations exist, Cr3+ and Ga3+, which are essentially twins; they possess identical charge, nearly identical radii (0.615Å for Cr3+ and 0.62Å for Ga3+), and very similar dipole polarizability (1.45Å3for Cr3+ and 1.50Å...

We hereby approve the thesis/dissertation of ____________________________________________________... more We hereby approve the thesis/dissertation of ______________________________________________________ candidate for the ________________________________degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________

Physics of the Earth and Planetary Interiors, 2009

a b s t r a c t Trivalent cations in periclase are attracted to cation vacancies and these defect... more a b s t r a c t Trivalent cations in periclase are attracted to cation vacancies and these defects tend to associate on adjacent sites to form mobile pairs. A theory has been developed to describe the concentration-dependent diffusion of Al in the presence of Al-vacancy pairs, and has been applied to experiments conducted at 1577-2273 K and 1 atm to 25 GPa. In all but one experiment, the Gibbs free energy of binding, inferred from the diffusion profiles, is between −44 and −60 kJ/mol, with an average value of −50 kJ/mol. The absolute value of the entropy of binding is constrained to be less than 50 J mol −1 K −1 , and the volume of binding is constrained to be between −1.8 and 0 cm 3 /mol. The diffusion coefficient of the Al-vacancy pair can be described by the equation D 2 = D 2,0 exp(−(E + PV)/RT), with E = 213 ± 32 kJ/mol, V = 3.22 ± 0.25 cm 3 /mol, and log 10 D 2,0 = −6.17 ± 0.99 (in m 2 /s; all uncertainties 2 ). Calculations are presented for the diffusion of Al and Mg as functions of Al concentration, temperature and pressure.

Phys. Rev. B, 2011

Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is... more Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is essential to a complete understanding of the Earth's interior. Fe cation diffusion potentially controls many aspects of the distribution of Fe in the Earth's lower ...

Microscopy and Microanalysis, 2014

Pallasites are a unique group of meteorites consisting of a mixture of approximately equal propor... more Pallasites are a unique group of meteorites consisting of a mixture of approximately equal proportions of olivine grains in a matrix of Fe-Ni metal. These meteorites provide physical samples of the interior of a differentiated planetary body. As such, they provide direct geochemical clues to planetary differentiation processes. In this study, one large collaborative effort is undertaken to analyze a suite of 14 main-group pallasite specimens by several different instrumental analytical techniques in an attempt to provide a comprehensive picture of formation processes, temperatures and timescales. The suite of specimens chosen come from both the main group pallasites and the Eagle Station trio, and encompass a range of fayalite composition and of olivine shape and distribution.

Reviews in Mineralogy and Geochemistry, 2010

on diffusion in corundum, and this has been reviewed recently by . Wüstite is addressed here as a... more on diffusion in corundum, and this has been reviewed recently by . Wüstite is addressed here as a solid solution with periclase; for information on cation self-diffusion in the pure phase see and references therein. Diffusion in silica minerals is reviewed by .

Physics of the Earth and Planetary Interiors, 2010

Experiments were performed to determine concentration-dependent diffusion coefficients of Cr 3+ a... more Experiments were performed to determine concentration-dependent diffusion coefficients of Cr 3+ and Ga 3+ in periclase at temperatures of 1563-2273 K. Diffusion profiles measured in the quenched samples are consistent with a theoretical model in which the mobile species is a bound M 3+ -vacancy pair, and each profile was fitted to determine the binding energy and diffusion coefficient of the pair. Trivalent chromium-vacancy pairs diffuse more slowly than Ga 3+ -vacancy pairs, and with higher migration energy, 237 kJ/mol vs. 190 kJ/mol. Cation vacancies also bind less tightly to Cr 3+ than to Ga 3+ , with average binding free energies of −22 and −83 kJ/mol, respectively. At all concentrations and temperatures, Cr 3+ diffuses much more slowly than Ga 3+ , by up to two orders of magnitude. The differences between Cr 3+ and Ga 3+ cannot be explained by differences in ionic radius or dipole polarizability, but are consistent with the influence of the crystal field on the partially occupied 3d orbitals of Cr 3+ . The crystal field splitting stabilizes Cr 3+ on the octahedral cation site, increasing the energy required for Cr 3+ to exchange positions with an adjacent vacancy. It also makes Cr 3+ -vacancy pairs less favorable, with the presence of a nearest-neighbor vacancy disrupting the symmetry of the octahedral site, thus diminishing the crystal field stabilization. Trends in the diffusion of first-row divalent transition metals in periclase can also be explained by the crystal field effect. High-spin to low-spin transitions in Fe 2+ , Co 2+ or Mn 2+ would significantly enhance their crystal field stabilization in periclase, and if such spin transitions occur in the deep mantle, they would be expected to slow the diffusivity of these ions significantly, perhaps by several orders of magnitude.

Microscopy and Microanalysis, 2012

Earth and Planetary Science Letters, 2012

and sharing with colleagues.

Periclase is thought to comprise about 15-20% of the lower mantle, making it the second most abun... more Periclase is thought to comprise about 15-20% of the lower mantle, making it the second most abundant phase present after magnesium silicate perovskite. Because cation diffusivity in periclase is relatively rapid compared to magnesium silicate perovskite, it may control bulk transport processes in the lower mantle. It is expected that trivalent cations such as Fe3+ and Al3+ are dissolved in

Journal of Applied Physics, 2015

Double stage diamond anvil cells (DAC) of two designs have been assembled and tested. We used a s... more Double stage diamond anvil cells (DAC) of two designs have been assembled and tested. We used a standard symmetric DAC as a primary stage and CVD microanvils machined by a focused ion beam -as a second. We evaluated pressure, stress, and strain distributions in Au and Fe-Au samples as well as in secondary anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage anvil culet size. We found that the stress field generated by the second stage anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary anvil and by cupping of the first stage diamond anvil in the presented experimental designs. Also,

Fe cation diffusion plays a fundamental role for many processes in Earth's mantle involving c... more Fe cation diffusion plays a fundamental role for many processes in Earth's mantle involving chemical, isotopic and advective mass transfer, and can potentially control homogenization of mantle materials and equilibration of elements between the core and mantle. Present data on Fe transport in Fp is limited to pressures below the top of the lower mantle and therefore must be extrapolated to model lower mantle conditions. However, extrapolation of Fe diffusion properties from measurements under 35 GPa to lower mantle pressures is quite uncertain due to uncertainty in the Fe activation volume and its unknown pressure dependence. In particular, the existing diffusion data includes no information on the effect of the recently discovered Fe spin transition. In the present study we combine first principles methods with statistical diffusion models to compute the Fe2+ diffusivity in dilute Fe ferropericlase at lower mantle pressures and temperatures. Diffusivities are determined for pur...

Trivalent impurities govern cation vacancy concentrations in most minerals, and thus play a centr... more Trivalent impurities govern cation vacancy concentrations in most minerals, and thus play a central role in solid-state diffusion in the Earth. Periclase is the second most abundant mineral in the lower mantle and is a key to understanding creep and chemical exchange mechanisms. Although periclase is among the simplest of minerals, diffusion of trivalent cations is a complex process. Trivalent cations tend to bind to oppositely charged cation vacancies to form pairs, and in some cases higher-order complexes. Impurity-vacancy pairs are extremely mobile species; the continual presence of a vacancy adjacent to the trivalent impurity allows it to move through the lattice much more rapidly than it would in the absence of binding. We have performed experiments on diffusion of Ga, Sc, Y and Cr in periclase, and developed a theoretical approach to extract the binding energy and impurity-vacancy pair diffusivity from the experimental diffusion profiles. Experiments were performed in an open ...

Geochmica et Cosmochimica Acta

Recent experimental results on diffusion of Ga3+ and Cr3+ in periclase indicate that the electron... more Recent experimental results on diffusion of Ga3+ and Cr3+ in periclase indicate that the electronic structure of transition metal cations has a strong influence on their diffusivity (Crispin and Van Orman, 2010). Transition metal cations with partially filled d-orbitals are stabilized on octahedral sites by the crystal field effect, which increases the energy barrier for the migration of cations to adjacent vacancies. A previous study of divalent transition metals (Wuensch and Vasilos, 1962) found that the diffusivity increased in the order Ni

Diffusion in minerals is the rate-limiting step in many mass transport processes that are fundame... more Diffusion in minerals is the rate-limiting step in many mass transport processes that are fundamental to geochemistry and geophysics. Thus, there has been a long-standing interest in finding theoretical or empirical relationships that relate the diffusion coefficient in a mineral to well-known ionic properties such as radius and charge. In many silicate minerals the diffusion coefficient is negatively correlated with ionic charge. In periclase, and some other minerals with a strong component of ionic bonding, highly charged cations diffuse rapidly due to their association with cation vacancies. Experiments on Al3+ diffusion in MgO have been performed over a wide range of pressure (1 atm to 25 GPa) and temperature (1573 to 2273 K), and the association energy and Al- vacancy pair diffusivity inferred from each by applying a simple defect interaction model to the diffusion profiles. The binding energy for all but one experiment is in the range 0.45-0.62 eV, and shows no clear dependenc...

Periclase is the second most abundant mineral in Earth's lower mantle and is a key to underst... more Periclase is the second most abundant mineral in Earth's lower mantle and is a key to understanding chemical exchange mechanisms and diffusive length scales at the core-mantle boundary. The crystal field effect has long been known to influence the partitioning of first-row transition metals in minerals, but its influence on diffusion has not previously been considered. Transition metal cations with partially filled d-orbitals are stabilized on octahedral sites by the crystal field effect; this crystal field stabilization may increase the energy barrier for the migration of cations to adjacent vacancies. To investigate the influence of the crystal field effect on diffusion in periclase, ideally one would hold all variables constant except for electronic structure. Two cations exist, Cr3+ and Ga3+, which are essentially twins; they possess identical charge, nearly identical radii (0.615Å for Cr3+ and 0.62Å for Ga3+), and very similar dipole polarizability (1.45Å3for Cr3+ and 1.50Å...

We hereby approve the thesis/dissertation of ____________________________________________________... more We hereby approve the thesis/dissertation of ______________________________________________________ candidate for the ________________________________degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________

Physics of the Earth and Planetary Interiors, 2009

a b s t r a c t Trivalent cations in periclase are attracted to cation vacancies and these defect... more a b s t r a c t Trivalent cations in periclase are attracted to cation vacancies and these defects tend to associate on adjacent sites to form mobile pairs. A theory has been developed to describe the concentration-dependent diffusion of Al in the presence of Al-vacancy pairs, and has been applied to experiments conducted at 1577-2273 K and 1 atm to 25 GPa. In all but one experiment, the Gibbs free energy of binding, inferred from the diffusion profiles, is between −44 and −60 kJ/mol, with an average value of −50 kJ/mol. The absolute value of the entropy of binding is constrained to be less than 50 J mol −1 K −1 , and the volume of binding is constrained to be between −1.8 and 0 cm 3 /mol. The diffusion coefficient of the Al-vacancy pair can be described by the equation D 2 = D 2,0 exp(−(E + PV)/RT), with E = 213 ± 32 kJ/mol, V = 3.22 ± 0.25 cm 3 /mol, and log 10 D 2,0 = −6.17 ± 0.99 (in m 2 /s; all uncertainties 2 ). Calculations are presented for the diffusion of Al and Mg as functions of Al concentration, temperature and pressure.

Phys. Rev. B, 2011

Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is... more Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is essential to a complete understanding of the Earth's interior. Fe cation diffusion potentially controls many aspects of the distribution of Fe in the Earth's lower ...

Microscopy and Microanalysis, 2014

Pallasites are a unique group of meteorites consisting of a mixture of approximately equal propor... more Pallasites are a unique group of meteorites consisting of a mixture of approximately equal proportions of olivine grains in a matrix of Fe-Ni metal. These meteorites provide physical samples of the interior of a differentiated planetary body. As such, they provide direct geochemical clues to planetary differentiation processes. In this study, one large collaborative effort is undertaken to analyze a suite of 14 main-group pallasite specimens by several different instrumental analytical techniques in an attempt to provide a comprehensive picture of formation processes, temperatures and timescales. The suite of specimens chosen come from both the main group pallasites and the Eagle Station trio, and encompass a range of fayalite composition and of olivine shape and distribution.

Reviews in Mineralogy and Geochemistry, 2010

on diffusion in corundum, and this has been reviewed recently by . Wüstite is addressed here as a... more on diffusion in corundum, and this has been reviewed recently by . Wüstite is addressed here as a solid solution with periclase; for information on cation self-diffusion in the pure phase see and references therein. Diffusion in silica minerals is reviewed by .

Physics of the Earth and Planetary Interiors, 2010

Experiments were performed to determine concentration-dependent diffusion coefficients of Cr 3+ a... more Experiments were performed to determine concentration-dependent diffusion coefficients of Cr 3+ and Ga 3+ in periclase at temperatures of 1563-2273 K. Diffusion profiles measured in the quenched samples are consistent with a theoretical model in which the mobile species is a bound M 3+ -vacancy pair, and each profile was fitted to determine the binding energy and diffusion coefficient of the pair. Trivalent chromium-vacancy pairs diffuse more slowly than Ga 3+ -vacancy pairs, and with higher migration energy, 237 kJ/mol vs. 190 kJ/mol. Cation vacancies also bind less tightly to Cr 3+ than to Ga 3+ , with average binding free energies of −22 and −83 kJ/mol, respectively. At all concentrations and temperatures, Cr 3+ diffuses much more slowly than Ga 3+ , by up to two orders of magnitude. The differences between Cr 3+ and Ga 3+ cannot be explained by differences in ionic radius or dipole polarizability, but are consistent with the influence of the crystal field on the partially occupied 3d orbitals of Cr 3+ . The crystal field splitting stabilizes Cr 3+ on the octahedral cation site, increasing the energy required for Cr 3+ to exchange positions with an adjacent vacancy. It also makes Cr 3+ -vacancy pairs less favorable, with the presence of a nearest-neighbor vacancy disrupting the symmetry of the octahedral site, thus diminishing the crystal field stabilization. Trends in the diffusion of first-row divalent transition metals in periclase can also be explained by the crystal field effect. High-spin to low-spin transitions in Fe 2+ , Co 2+ or Mn 2+ would significantly enhance their crystal field stabilization in periclase, and if such spin transitions occur in the deep mantle, they would be expected to slow the diffusivity of these ions significantly, perhaps by several orders of magnitude.

Microscopy and Microanalysis, 2012

Earth and Planetary Science Letters, 2012

and sharing with colleagues.

Periclase is thought to comprise about 15-20% of the lower mantle, making it the second most abun... more Periclase is thought to comprise about 15-20% of the lower mantle, making it the second most abundant phase present after magnesium silicate perovskite. Because cation diffusivity in periclase is relatively rapid compared to magnesium silicate perovskite, it may control bulk transport processes in the lower mantle. It is expected that trivalent cations such as Fe3+ and Al3+ are dissolved in

Journal of Applied Physics, 2015

Double stage diamond anvil cells (DAC) of two designs have been assembled and tested. We used a s... more Double stage diamond anvil cells (DAC) of two designs have been assembled and tested. We used a standard symmetric DAC as a primary stage and CVD microanvils machined by a focused ion beam -as a second. We evaluated pressure, stress, and strain distributions in Au and Fe-Au samples as well as in secondary anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage anvil culet size. We found that the stress field generated by the second stage anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary anvil and by cupping of the first stage diamond anvil in the presented experimental designs. Also,