...Claus H. Rüscher Abstract Temperature-dependent absorption investigations between 10 and 823 K reveal photon-assisted hopping (PAH) of small polarons in biotites as the dominating excitation in the near-infrared spectral range. These data show a transfer of oscillator strength of the PAH of small...

... that charge transport by small polaron is reduced in mixed-spin ferropericlase, providing fundamental insights into the factor-of-three lower electrical conductivity of ferropericlase at ~50–70 GPa. All high-pressure experiments were performed using symmetrical DACs equipped with diamond pairs featuring...

..., quartz, and tourmaline. The color centers in these minerals are often related to O − hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil...

... in wadsleyite the electrical conductivity increases at a rate higher than observed in previous studies. The activation enthalpy in the temperature range studied where proton conduction dominates is low (0.66 eV) suggesting an inevitable crossover to small polaron conduction at moderately higher temperatures...

... in the lithosphere and, in particular, the development of high conductivity in the Earth’s interior. Recently, we have shown that at elevated temperatures, C Fe-bearing amphiboles with a vacant A site develop two types of charge carriers: (1) small polarons and (2) delocalized H + ions. To elucidate the effect...

... are assumed to exchange their oxidation states dynamically between 3+ and 4+ in a time ratio of ~3:1, forming a polaron centered at a Mn 4 O 4 heterocubane cluster with orbital and spin orders. The high-temperature cubic form contains an inherent positional disordering of oxygen ions. The effect...

... , C.H. ( 2012 ) Temperature-dependent absorption of biotite: Small-polaron hopping and other fundamental electronic excitations . European Journal of Mineralogy , 24 , 815 – 820 , https://doi.org/10.1127/0935-1221/2012/0024-2200 . Sherman , D.M. ( 1987a ) Molecular orbital (SCF-Xα-SW...

... absorption spectra see e.g. Rossman (2024). For the spectra contained 247 within the current work, in samples where the splitting is small, effectively, only one component 248 around ~900-1000 nm is easily distinguished by inspection alone; in samples where the splitting is 249 larger, an obvious second...

... of modifier Fe 2+ with atmospheric oxygen to create a modifier Fe 3+ (i.e., h · ) produces a structural distortion (relative to the initial state). In the crystalline state, this distortion is referred to as a “small polaron;” the description is directly applicable to the amorphous state. In Figure 3a , we...

... on structural data (Lottermoser et al.), and the ordering of Al in Al-rich phlogopite (Langner & Fechtelkord). Rüscher presents important new results on the role of polarons as charge carriers in biotites. High-pressure experimental studies include the investigation of optical absorption in V 3+ -bearing...

..., activation energies for conductivity vary smoothly with composition and increase rapidly toward the pyrope end-member composition, where it reaches a value of 2.5 eV. The results are consistent with an electrical conductivity mechanism involving small polaron mobility in the Fe-bearing garnets at 10 GPa...

... temperature. The isotope diffusion coefficients for hydrogen in nominally anhydrous minerals are regarded as impurity tracer diffusion coefficients, which refer to diffusion of species at infinitely small dilution, while isotope diffusion coefficients for hydrous minerals refer to self-diffusion of intrinsic...

..., for anhydrous single-crystal olivine (0.18) and olivine aggregates (0.096), these q values are positive and totally different, due to the Fe 2+ →Fe 3+ small-polaron hopping conduction ( Schock et al. , 1989 ; Dai et al. , 2010 ). The negative oxygen-fugacity exponential factor derived here is consistent...

... at the micrometer-scale, such as the Mössbauer milliprobe ( McCammon 1994 ; Mc-Cammon et al. 1991 ) and Fe K -edge X-ray absorption near-edge spectroscopy (XANES) ( Wilke et al. 2001 ; Berry et al. 2003 ; Magnien et al. 2004 ). Alternatively, we use Raman spectroscopy to quantify the redox state of Fe at small...

... sections; one side of the crystal has 7.7 ± 1.1 ppm and the other 13.9 ± 2.3 ppm. The reason for this behavior is unknown; it may be that the Czochralski growth method led to some minor sector zoning in the original crystal. The small amount of Fe (10–50 ppm) is likely from contamination in the gas-mixing...

... of the sample. In our case one-dimensional diffusion is justified, as the thickness of the sample is usually very small compared to the surface area (crystal faces) where absorption/diffusion is measured. The diffusion is expected to be near isotropic due to low Fe content ( Ingrin et al. , 1995 ; Hercule...

... listed in Supplemental 1 Table S2. As commonly observed in natural clinopyroxene (e.g., Skogby et al. 1990 ), four groups of OH absorption bands are found in the 10 samples: 3620–3640 cm –1 (group 1), 3530–3540 cm –1 (group 2), 3460 cm –1 (group 3), and 3360 cm –1 (group 4) as shown...

... to synthetic analogues with X Fe/(Fe + Mg) < 0.02 ( Ingrin et al. , 1995 ; Hercule & Ingrin, 1999 ; Woods et al. , 2000 ; Sundvall et al. , 2009 ). This difference can be explained as reaction (1) leads to a flux of electron holes (polarons) during the change in valence state of Fe...

... been reported ( Ingrin et al. 2014 ; Crépisson et al. 2014 ). Hydrogen with different incorporation mechanisms is expected to have different properties, such as diffusivities ( Padrón-Navarta et al. 2014 ), infrared absorption coefficients ( Kovàcs et al. 2010 ), and solubility ( Ingrin et al. 2013...