We report on the structural evolution, spin phonon interactions, and magnetoelastic effects in bulk LaFeO3 perovskite across its antiferromagnetic transition. We found that while the lattice constants exhibit slight deviations at the Neel temperature(TN), due to spin phonon interactions, individual interatomic bonds display distinct behavior. The octahedral B site basal plane, involving oxygen ion pairs that mediate superexchange interactions, displays bond contraction (or elongation) assimilable to the observed in x ray diffraction for negative thermal expansion. These bond deviations reach a singular point near TN, where a sharp change in bond length is observed. A similar abrupt change is also detected in the nearest neighbor La O2 basal plane distances, which we interpret as arising from ion size differences within the 3d 2p hybridized states associated with the superexchange mechanism. High-resolution SXRD measurements of the c-axis Fe3+ O1 and La3+ O1 apex distances reveal a distinct inflection at the Neel temperature. This behavior supports the role of lattice distortions and crystal field modifications in the emergence of non collinear weak ferromagnetism in RFeO3 (R = rare earth) perovskites. Furthermore, our SXRD patterns show an increase in diffraction line intensities peaking at TN, suggesting a straightforward indicator for spin-phonon interactions that also resolves into lattice metastability deduced by nonlinear thermal expansion in the paramagnetic phase. Preliminary results across the full RFeO3 (R = rare earth) series indicate a shared structural framework among all members, potentially offering insights into previously inconclusive structural interpretations in oxides with common octahedral sublattices.

We report on zone center THz excitations of non-Jahn Teller LaFeO_3, PrFeO_3, ErFeO_3, and LuFeO_3 distorted perovskites under external magnetic fields up 7 T. Low temperature-low energy absorptions of LaFeO_3 show antiferromagnetic and ferromagnetic quasimagnons at ωAFM 31.4 and ωFM 26.7 cm^-1 in the Γ4 (Gx, Ay, Fz) representation. LuFeO_3 is characterized by zero field magnetic resonances at ωAFM 26.3 cm^-1 and ωFM 22.4 cm^-1 in addition to Fe^3+ Zeeman-split crystal field (CF) 6A_1 ground transitions at 10.4 cm^-1 triggered by structural deviations induced by smaller Lu 4f^14. This local non-centrosymmetric departure is also found in ErFeO_3 (Kramers 4f^11 Er^3+ (4I15/2); Γ2 (Fx, Cy, Gz) <TSR 93 K), but with the 4 cm^-1 Fe^3+ Zeeman branching strongly biased toward higher energies. Quasimagnons at ωAFM 31.5 cm^-1 and ωFM 21.5 cm^-1 in ErFeO_3 do not undergo field induced band splits but a 13-fold increase in the antiferro (ωAMF) /ferro(ωAFM) intensity ratio. There is a remarkable field-dependent CF matching population balance between Fe^3+ higher and Er^3+ lower Zeeman branches. Antiferro- and ferro- resonances in PrFeO_3 turn much broader as non-Kramers Pr^3 introduces ligand changes at the A site leading into near degeneracy the antiferromagnetic mode and the lowest Pr^3+ CF transition. We conclude that low energy excitations in RFeO_3 (R=rare earth) strongly depend on the lanthanide ionic size. Minute lattice displacements also underlie considering non-centrosymmetric the most distorted RFeO_3 (R=rare earth). Changes triggered by the smaller rare earth and the nonlinear intrinsic oxygen ion polarizability provide grounds for interplay of ionic and electronic interactions yielding ferroelectric spontaneous polarization.

We report on zone center THz excitations of non-Jahn Teller LaFeO$_3$, PrFeO$_3$, ErFeO$_3$, and LuFeO$_3$ distorted perovskites under external magnetic fields up 7 T. Low temperature-low energy absorptions of LaFeO$_3$ show antiferromagnetic and ferromagnetic quasimagnons at $\omega$AFM ~31.4 and $\omega$FM ~26.7 cm$^{-1}$ in the $\Gamma$4 (Gx, Ay, Fz) representation. LuFeO$_3$ is characterized by zero field magnetic resonances at $\omega$AFM ~26.3 cm$^{-1}$ and $\omega$FM ~22.4 cm$^{-1}$ in addition to Fe$^{3+}$ Zeeman-split crystal field (CF) 6A$_1$ ground transitions at ~10.4 cm$^{-1}$ triggered by structural deviations induced by smaller Lu 4f$^{14}$. This local non-centrosymmetric departure is also found in ErFeO$_3$ (Kramers 4f$^{11}$ Er$^{3+}$ (4I15/2); {\Gamma}2 (Fx, Cy, Gz)

We report on zone center terahertz excitations of non-Jahn Teller ${\mathrm{LaFeO}}_{3}, {\mathrm{PrFeO}}_{3}, {\mathrm{ErFeO}}_{3}$, and ${\mathrm{LuFeO}}_{3}$ distorted perovskites under external magnetic fields up 7 T. Our measurements on low-temperature/low-energy absorptions of ${\mathrm{LaFeO}}_{3}$ show quasiantiferromagnetic (q-AFM) and quasiferromagnetic (q-FM) magnons at ${\ensuremath{\omega}}_{q\mathrm{AFM}}\ensuremath{\sim}31.4\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ and ${\ensuremath{\omega}}_{q\mathrm{FM}}\ensuremath{\sim}26.7\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ in the ${\mathrm{\ensuremath{\Gamma}}}_{4}\phantom{\rule{0.28em}{0ex}}({G}_{x},\phantom{\rule{0.28em}{0ex}}{A}_{y},\phantom{\rule{0.28em}{0ex}}{F}_{z})$ representation with near degeneracy linearly lifted by the field. ${\mathrm{LuFeO}}_{3}$ is characterized by zero-field magnetic resonances at ${\ensuremath{\omega}}_{q\mathrm{AFM}}\ensuremath{\sim}26.3\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ and ${\ensuremath{\omega}}_{q\mathrm{FM}}\ensuremath{\sim}22.4\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ in addition to ${\mathrm{Fe}}^{3+}$ Zeeman-split crystal field (CF) $6{\mathrm{A}}_{1}$ ground transitions at $\ensuremath{\sim}10.4\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ triggered by subtle structural deviations induced by the $\mathrm{Lu}\phantom{\rule{0.28em}{0ex}}4{f}^{1}4$ smaller ionic radius at the A site. This local quasinoncentrosymmetric departure is also found in ${\mathrm{ErFeO}}_{3}$ (Kramers $4{f}^{11} {\mathrm{Er}}^{3+}\phantom{\rule{0.28em}{0ex}}(^{4}\mathrm{I}_{15/2})$; ${\mathrm{\ensuremath{\Gamma}}}_{2}({F}_{x},\phantom{\rule{0.28em}{0ex}}{C}_{y},\phantom{\rule{0.28em}{0ex}}{G}_{z})<{T}_{\mathrm{SR}}\ensuremath{\sim}93\phantom{\rule{0.28em}{0ex}}\mathrm{K})$ but with the $\ensuremath{\sim}4\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1} {\mathrm{Fe}}^{3+}$ Zeeman branching strongly biased toward higher energies due to $3d\text{\ensuremath{-}}4f$ exchange. Magnons at ${\ensuremath{\omega}}_{q\mathrm{AFM}}\ensuremath{\sim}31.5\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ and ${\ensuremath{\omega}}_{q\mathrm{FM}}\ensuremath{\sim}21.5\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ in ${\mathrm{ErFeO}}_{3}$ do not undergo field-induced band splits but a 13-fold increase in the q-AFM (${\ensuremath{\omega}}_{q\mathrm{AMF}}$)/q-FM (${\ensuremath{\omega}}_{q\mathrm{AFM}}$) intensity ratio. There is a remarkable field-dependent CF matching population balance between ${\mathrm{Fe}}^{3+}$ higher and ${\mathrm{Er}}^{3+}$ lower Zeeman branches. The ${\mathrm{Er}}^{3+}\phantom{\rule{0.28em}{0ex}}(^{4}\mathrm{I}_{15/2})$ multiplet, at the 49.5, 110.5, and $167.3\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$, coincides with external lattice mode frequencies, suggesting strong lattice-driven spin-phonon interactions. Far-infrared absorption ratios under mild external fields reveal magnetic dependence only for those zone-center phonons involving moving magnetic ions. Overall, our results support the viability of magnetic state manipulation by phonons. Quasiantiferroresonances and quasiferroresonances in ${\mathrm{PrFeO}}_{3}$ turn much broader as non-Kramers ${\mathrm{Pr}}^{3}$ introduces ligand changes at the A site, leading into near degeneracy the q-AFM mode and the lowest ${\mathrm{Pr}}^{3+}$ CF transition. They merge into a single broad mostly unresolved feature at 7 T. We conclude that low-energy excitations in $R{\mathrm{FeO}}_{3}$ ($R=\mathrm{rare}\phantom{\rule{0.28em}{0ex}}\mathrm{earth}$) strongly depend on the lanthanide ionic size, thus indivisibly tied to the mechanism associated with the origin of canted FM. In addition, minute lattice displacements also underlie considering noncentrosymmetric the most distorted $R{\mathrm{FeO}}_{3}$ ($R=\mathrm{rare}\phantom{\rule{0.28em}{0ex}}\mathrm{earth}$). In these perovskites, the changes triggered in the lattice by the smaller rare earth and the nonlinear intrinsic oxygen ion polarizability, known to drive lattice instabilities, provide grounds for interplay of ionic and electronic interactions yielding ferroelectric spontaneous polarization.

We report on zone center THz excitations of non-Jahn Teller LaFeO$_3$, PrFeO$_3$, ErFeO$_3$, and LuFeO$_3$ distorted perovskites under external magnetic fields up 7 T. Low temperature-low energy absorptions of LaFeO$_3$ show antiferromagnetic and ferromagnetic quasimagnons at $\omega$AFM ~31.4 and $\omega$FM ~26.7 cm$^{-1}$ in the $\Gamma$4 (Gx, Ay, Fz) representation. LuFeO$_3$ is characterized by zero field magnetic resonances at $\omega$AFM ~26.3 cm$^{-1}$ and $\omega$FM ~22.4 cm$^{-1}$ in addition to Fe$^{3+}$ Zeeman-split crystal field (CF) 6A$_1$ ground transitions at ~10.4 cm$^{-1}$ triggered by structural deviations induced by smaller Lu 4f$^{14}$. This local non-centrosymmetric departure is also found in ErFeO$_3$ (Kramers 4f$^{11}$ Er$^{3+}$ (4I15/2); {\Gamma}2 (Fx, Cy, Gz)<TSR ~93 K), but with the ~4 cm$^{-1}$ Fe$^{3+}$ Zeeman branching strongly biased toward higher energies. Quasimagnons at $\omega$AFM ~31.5 cm$^{-1}$ and $\omega$FM ~21.5 cm$^{-1}$ in ErFeO$_3$ do not undergo field induced band splits but a 13-fold increase in the antiferro ($\omega$AMF) /ferro($\omega$AFM) intensity ratio. There is a remarkable field-dependent CF matching population balance between Fe$^{3+}$ higher and Er$^{3+}$ lower Zeeman branches. Antiferro- and ferro- resonances in PrFeO$_3$ turn much broader as non-Kramers Pr$^3$ introduces ligand changes at the A site leading into near degeneracy the antiferromagnetic mode and the lowest Pr$^{3+}$ CF transition. We conclude that low energy excitations in RFeO$_3$ (R=rare earth) strongly depend on the lanthanide ionic size. Minute lattice displacements also underlie considering non-centrosymmetric the most distorted RFeO$_3$ (R=rare earth). Changes triggered by the smaller rare earth and the nonlinear intrinsic oxygen ion polarizability provide grounds for interplay of ionic and electronic interactions yielding ferroelectric spontaneous polarization.

We report on zone center terahertz excitations of non-Jahn Teller LaFeO3, PrFeO3, ErFeO3, and LuFeO3 distorted perovskites under external magnetic fields up 7 T. Our measurements on low-temperature/low-energy absorptions of LaFeO3 show quasiantiferromagnetic (q-AFM) and quasiferromagnetic (q-FM) magnons at omega(qAFM) similar to 31.4 cm(-1) and omega(qFM)similar to 26.7 cm(-1) in the Gamma(4) (G(x), A(y), F-z) representation with near degeneracy linearly lifted by the field. LuFeO3 is characterized by zero-field magnetic resonances at omega(qAFM) similar to 26.3 cm(-1) and omega(qFM) similar to 22.4 cm(-1) in addition to Fe3+ Zeeman-split crystal field (CF) 6A(1) ground transitions at similar to 10.4 cm(-1) triggered by subtle structural deviations induced by the Lu 4f(1)4 smaller ionic radius at the A site. This local quasinoncentrosymmetric departure is also found in ErFeO3 (Kramers 4f(11) Er3+ (I-4(15/2)); Gamma(2)(F-x, C-y, G(z)) < T-SR similar to 93 K) but with the similar to 4 cm(-1) Fe3+ Zeeman branching strongly biased toward higher energies due to 3d-4f exchange. Magnons at omega(qAFM) similar to 31.5 cm(-1) and omega(qFM) similar to 21.5 cm(-1) in ErFeO3 do not undergo field-induced band splits but a 13-fold increase in the q-AFM (omega(qAMF))/q-FM (omega(qAFM)) intensity ratio. There is a remarkable field-dependent CF matching population balance between Fe3+ higher and Er3+ lower Zeeman branches. The Er3+ (I-4(15/2)) multiplet, at the 49.5, 110.5, and 167.3 cm(-1), coincides with external lattice mode frequencies, suggesting strong lattice-driven spin-phonon interactions. Far-infrared absorption ratios under mild external fields reveal magnetic dependence only for those zone-center phonons involving moving magnetic ions. Overall, our results support the viability of magnetic state manipulation by phonons. Quasiantiferroresonances and quasiferroresonances in PrFeO3 turn much broader as non-Kramers Pr-3 introduces ligand changes at the A site, leading into near degeneracy the q-AFM mode and the lowest Pr3+ CF transition. They merge into a single broad mostly unresolved feature at 7 T. We conclude that low-energy excitations in RFeO3 (R = rare earth) strongly depend on the lanthanide ionic size, thus indivisibly tied to the mechanism associated with the origin of canted FM. In addition, minute lattice displacements also underlie considering noncentrosymmetric the most distorted RFeO3 (R = rare earth). In these perovskites, the changes triggered in the lattice by the smaller rare earth and the nonlinear intrinsic oxygen ion polarizability, known to drive lattice instabilities, provide grounds for interplay of ionic and electronic interactions yielding ferroelectric spontaneous polarization.

We report the temperature dependent THz to mid-infrared response of hexagonal-ErMnO3 using absorption, reflectivity, and emissivity techniques from 2 K to 1700 K. At low temperatures, lowest frequency vibrational modes coexist with paramagnon excitations associated with well-defined crystal field Rare Earth pure magnetic replicas in an intriguing phonon-magnetic convergence. Increasing the temperature, a number of vibrational bands close to the space group predicted undergo profile broadening and softening. In particular, a distinctive set of bands in the 288-329 cm-1 (300 K) range has a component whose profile is carrier screened becoming nearly fully blurred in the intermediate phase between ~830 K and ~1500 K. Below TC ~830 K this asymmetric band further splits as spin phonon interaction and the tripling of the unit cell takes place revealing a delicate balance of long- and short-range interactions. Ambient Raman scattering brings up evidence of a Frohlich resonance due to Coulomb interactions between carriers and the macroscopic field of the longitudinal optical phonon mode. We found it is dynamically correlated to the hexagonal c-axis negative thermal expansion. Mid-infrared (MIR) optical conductivity show that also plays a role in small polarons and mediates in high temperature this http URL higher temperatures a low frequency Drude contribution is triggered by electron hopping signaling an insulator-metal phase transition at ~1600 K while the MIR response suggests coexistence between single small polarons and bipolarons. We draw a parallel with improper ferroelectrics sustaining a lattice incommensurate intermediate phase and unit cell tripling. We argue that in the h-RMnO3 (R=Rare Earth, Y) family of compounds the intermediate phase be considered incommensurate with onset at TINC ~1500 K and ferroelectric lock-in at TC ~830 K delimiting this regime in h-ErMnO3.

Two polymorphs of tetrathiafulvalene chloranilic acid (TTF-CAH2) have been synthesized by mechanochemistry. The previously known "ionic" polymorph (form I) was prepared by liquid-assisted grinding (LAG) using various highly polar solvents as well as protic but moderately polar solvents, such as alcohols of one to four carbon atoms. A new TTF-CAH2 polymorph (form II) was obtained by LAG and slurry mechanochemistry using aprotic, low-polarity solvents, as well as nonpolar solvents and neat grinding. The crystal structure of the new TTF-CAH2 polymorph was determined from the combined analysis of synchrotron powder X-ray diffraction and neutron powder diffraction data at room temperature. The material displays segregated stacks of TTF and CAH2 molecules. Fourier transform infrared spectroscopy as a function of the temperature (10-300 K) indicates that TTF-CAH2 form II is an electrical semiconductor with a small band gap of ∼0.115 eV (versus ∼0.146 eV for the "ionic" form I), and there is no indication of phase transitions in that temperature interval. The examination of the frequency regions wherein the absorption bands of TTF and TTF+• species occur suggests that TTF-CAH2 form II is most likely a neutral phase.

We report on the high-temperature evolution of far- and mid-infrared reflectivity and emissivity spectra of ambient orthorhombic ErMnO3 from 12 K to sample decomposition above 1800 K. At low temperatures the number of phonons agrees with the predictions for orthorhombic space group D-2h(16)-Pbnm (Z = 4) and coexists with a paramagnon spin resonance and rare-earth crystal-field transitions. Increasing the temperature, a number of vibrational bands undergo profile broadening and softening approaching the orbital disordered phase where the orthorhombic O' lower-temperature cooperative phase coexists with cubic-orthorhombic O. O-ErMnO3 undergoes a first-order order-disorder transition into the perovskite cubic phase at T-cubic similar to 1329 K +/- 20 K where the three triple degenerate phonons allowed by the space group Pm-3m (Z = 1) are identified. At about 800 K, a quantitative small polaron analysis of the orthorhombic midinfrared real part optical conductivity shows that antisymmetric and symmetric breathing modes sustain the strongest electron-phonon interactions. Above T-cubic the bipolaron fingerprint profile is the midinfrared dominant and only feature. Its appearance correlates with the localized screening of the highest vibrational mode reststrahlen band. We propose that the longitudinal optical mode macroscopic field screening is a consequence of dynamically sharing S disproportioned e(g) electrons hovering over the Jahn-Teller distorted octahedral dimer {Mn(Q(JT))(3+delta)[Mn(Q(JT))[3](-)(delta)]O-6/2}(2). A thermal driven insulator-metal transition is detected with onset similar to 1600 K. We also address the occurrence of an inhomogeneity induced terahertz band result of heating the samples in dry air, triggering Mn3+ Mn4+ double exchange, under the presence of Mn4+ smaller ions stabilizing the orthorhombic lattice.

We report on THz absorption spectroscopy combined with high magnetic fields of polycrystalline RCrO3 (R= Pr, Sm, Er) aiming understanding spin wave resonances at their low temperature magnetic phases. Our measurements show that the temperature, and the implicit anisotropies at which the Cr3+ spin reorientation at TSR takes place, are determinant on the ferromagnetic-like (FM) and the antiferromagnetic-like (AFM) spin modes being optically active. It is found that they are dependent on Rare Earth 4f moment and ion size. We also studied temperature and field dependence of crystal field levels in the same spectroscopic region. Pr3+ non-Kramers emerges at 100 K and Zeeman splits. An observed absence of spin wave resonances in PrCrO3 is attributed to Pr3+ remaining paramagnetic. In SmCrO3 near cancelation of the spin and orbital moments is proposed as the possible reason for not detecting Sm3+ ground state transitions. Here, the FM and AFM resonant modes harden when the temperature decreases and split linearly on applied fields at 5 K and below. In ErCrO3 the Er3+ Kramers doublet becomes active at about the TSR onset. Each line further experiences Zeeman splitting under magnetic fields while an spin reversal induced by a 2.5 T field, back to the Gamma4 (Fz) from the Gamma1 phase at 2 K, produces a secondary splitting. The 5 K AFM and FM excitations in ErCrO3 have a concerted frequency-intensity temperature dependence and a shoulder pointing to the Er3+ smaller ion size also disrupting the two magnetic sublattice approximation . Both resonances reduce to one when the temperature is lowered to 2 K in the Gamma1 representation.

TTF-DDQ (DDQ= 2,3-dichloro-5,6-dicyano-p-benzoquinone) is an ionic and diamagnetic charge transfer salt. Polycrystalline powders of TTF-DDQ were obtained by three synthetic methods: solvent evaporation from MeCN solution (1), MeCN vapor digestion (2), and mechanochemistry (liquid assisted grinding with DMSO) (3). The analysis of the synchrotron X-ray powder diffraction data of 1 afforded the crystal structure, which is isomorphous to that of the black polymorph of TTF-CA (CA= chloranil). TTF-DDQ is composed of (TIT ')2 and (DDQ-')2 dimeric radical ions arranged in segregated columnar stacks, linked by weak hydrogen bonds. The Cl and CN substituents in DDQ are disordered, and this was modeled by Rietveld analysis.The FT-IR absorption spectra as a function of the temperature in the 300-10 K interval showed an absorption edge, indicating that TTF-DDQ is a semiconductor with a small band gap of (0.21 0.01) eV. The monotonous evolution of the FT-IR spectra denotes the absence of crystallographic phase transitions in the temperature interval studied, likely due to the thermodynamic stability of this packing motif compared to the less stable donor -acceptor alternating stacks; or the segregated, potentially conducting stacks. (C) 2016 Elsevier B.V. All rights reserved.

We report on x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) measurements of SmNiO3 from 20 K to 600 K and up to 38 GPa at the Ni K and Sm L3 edges. A multiple component pre-Ni K edge tail is understood, originating from 1 s transitions to 3d-4p states while a post-edge shoulder increases distinctively smoothly, at about the insulator to metal phase transition (TIM), due to the reduction of electron–phonon interactions as the Ni 3d and O 2p band overlap triggers the metallic phase. This effect is concomitant with pressure-induced Ni-O-Ni angle increments toward more symmetric Ni3+ octahedra of the rhombohedral R¯3c space group. Room temperature pressure-dependent Ni white line peak energies have an abrupt ∼3.10 ± 0.04 GPa valence discontinuity from non-equivalent Ni3+δ + Ni3–δ charge disproportionate net unresolved absorber turning at ∼TIM into Ni3+ of the orthorhombic Pbnm metal oxide phase. At 20 K the overall white line response, still distinctive at TIM ∼8.1 ± 0.6 GPa is much smoother due to localization. Octahedral bond contraction up to 38 GPa and at 300 K and 20 K show breaks in its monotonic increase at the different structural changes. The Sm L3 edge does not show distinctive behaviors either at 300 K or 20 K up to about 35 GPa but the perovskite Sm cage, coordinated to eight oxygen atoms, undergoes strong uneven bond contractions at intermediate pressures where we found the coexistence of octahedral and rhombohedral superexchange angle distortions. We found that the white line pressure-dependent anomaly may be used as an accurate alternative for delineating pressure–temperature phase diagrams.

We report on XANES and EXAFS measurements of SmNiO3 from 20 K to 600 K and up to 38 GPa at the Ni K- and Sm L3- edges. A multiple component pre- Ni K-edge tail is understood originating from 1s transitions to 3d-4p states while a post-edge shoulder increases distinctively smooth, at about the insulator to metal phase transition (TIM), due to the reduction of electron-phonon interactions as the Ni 3d and O 2p band overlap triggers the metallic phase. This effect is concomitant with pressure induced Ni-O-Ni angle increments toward more symmetric Ni3+ octahedra of the rhombohedral R-3c space group. Room temperature pressure dependent Ni white line peak energies have an abrupt ~3.10+-0.04 GPa Pa valence discontinuity from non-equivalent Ni3+{\delta} + Ni3-{\delta} charge disproportionate net unresolved absorber turning at ~TIM into Ni3+ of the orthorhombic Pbnm metal oxide phase. At 20 K the overall white line response, still distinctive at TIM ~8.1+-0.6 GPa is much smoother due to localization. Octahedral bond contraction up to 38 GPa and at 300 K and 20 K show breaks in its monotonic increase at the different structural changes. The Sm L3-edge does not show distinctive behaviors either at 300 K or 20 K up about 35 GPa but the perovskite Sm cage, coordinated to eight oxygen atoms, undergoes strong uneven bond contractions at intermediate pressures where we found coexistence of octahedral and rhombohedral superexchange angle distortions. We found that the white line pressure dependent anomaly may be used as an accurate alternative for delineating pressure-temperature phase diagrams.

Tetrathiafulvalene-chloranil (TTF-CA) was synthesized by two methods, liquid assisted grinding (LAG) and vapor digestion (VD), which largely reduce the use of reaction solvents. The effects of the small quantities of LAG solvent and solvent vapors in VD toward the formation of a particular TTF-CA product polymorph were studied from both tetrathiafulvalene forms (orange and brown) as reactants. It was concluded that a high solvent polarity index favors the formation of the ionic black polymorph of TTF-CA vs the quasi-neutral green form, whereas the crystal structure and crystal habit of the orange tetrathiafulvalene polymorph also favors the formation of the black TTF-CA. The crystal structure of the black TTF-CA was determined from synchrotron X-ray powder diffraction (XRPD), and it consists of dimerized TTF+center dot and CA(-center dot) radical ions, in agreement with room temperature magnetic susceptibility measurements indicating the material is diamagnetic. FT-IR showed that the compound is a semiconductor with a small. band gap of similar to 0.198 eV and it remains ionic at low temperatures. The latter was confirmed by XRPD showing the black TTF-CA does not undergo a phase transition in the range 298-20 K. Band structure calculations are in good agreement with the measured band gap.