Liam Nagle Cocco

All Publications

• Spin-Glass States Generated in a van der Waals Magnet by Alkali-Ion Intercalation. Advanced materials (Deerfield Beach, Fla.) Khan, S., Aw, E. S., Nagle-Cocco, L. A., Sud, A., Ghosh, S., Subhan, M. K., Xue, Z., Freeman, C., Sagkovits, D., Gutiérrez-Llorente, A., Verzhbitskiy, I., Arroo, D. M., Zollitsch, C. W., Eda, G., Santos, E. J., Dutton, S. E., Bramwell, S. T., Howard, C. A., Kurebayashi, H. 2024: e2400270

  Abstract

  Tuning magnetic properties in layered van der Waals (vdW) materials has captured significant attention due to the efficient control of ground states by heterostructuring and external stimuli. Electron doping by electrostatic gating, interfacial charge transfer, and intercalation is particularly effective in manipulating the exchange and spin-orbit properties, resulting in a control of Curie temperature (TC) and magnetic anisotropy. Here, an uncharted role of intercalation is discovered to generate magnetic frustration. As a model study, Na atoms are intercalated into the vdW gaps of pristine Cr2Ge2Te6 (CGT) where generated magnetic frustration leads to emerging spin-glass states coexisting with a ferromagnetic order. A series of dynamic magnetic susceptibility measurements/analysis confirms the formation of magnetic clusters representing slow dynamics with a distribution of relaxation times. The intercalation also modifies other macroscopic physical parameters including the significant enhancement of TC from 66 to 240 K and the switching of magnetic easy-hard axis direction. This study identifies intercalation as a unique route to generate emerging frustrated spin states in simple vdW crystals.

  View details for DOI 10.1002/adma.202400270

  View details for PubMedID 39036829

• Local Structure and Dynamics in MPt(CN)6 Prussian Blue Analogues. Chemistry of materials : a publication of the American Chemical Society Harbourne, E. A., Barker, H., Guéroult, Q., Cattermull, J., Nagle-Cocco, L. A., Roth, N., Evans, J. S., Keen, D. A., Goodwin, A. L. 2024; 36 (11): 5796-5804

  Abstract

  We use a combination of X-ray pair distribution function (PDF) measurements, lattice dynamical calculations, and ab initio density functional theory (DFT) calculations to study the local structure and dynamics in various MPt(CN)6 Prussian blue analogues. In order to link directly the local distortions captured by the PDF with the lattice dynamics of this family, we develop and apply a new "interaction-space" PDF refinement approach. This approach yields effective harmonic force constants, from which the (experiment-derived) low-energy phonon dispersion relations can be approximated. Calculation of the corresponding Grüneisen parameters allows us to identify the key modes responsible for negative thermal expansion (NTE) as arising from correlated tilts of coordination octahedra. We compare our results against the phonon dispersion relations determined using DFT calculations, which identify the same NTE mechanism.

  View details for DOI 10.1021/acs.chemmater.4c01013

  View details for PubMedID 38883430

  View details for PubMedCentralID PMC11170939

• Mechanochemically-induced glass formation from two-dimensional hybrid organic-inorganic perovskites. Chemical science Ye, C., Lampronti, G. I., McHugh, L. N., Castillo-Blas, C., Kono, A., Chen, C., Robertson, G. P., Nagle-Cocco, L. A., Xu, W., Stranks, S. D., Martinez, V., Brekalo, I., Karadeniz, B., Užarević, K., Xue, W., Kolodzeiski, P., Das, C., Chater, P., Keen, D. A., Dutton, S. E., Bennett, T. D. 2024; 15 (19): 7198-7205

  Abstract

  Hybrid organic-inorganic perovskites (HOIPs) occupy a prominent position in the field of materials chemistry due to their attractive optoelectronic properties. While extensive work has been done on the crystalline materials over the past decades, the newly reported glasses formed from HOIPs open up a new avenue for perovskite research with their unique structures and functionalities. Melt-quenching is the predominant route to glass formation; however, the absence of a stable liquid state prior to thermal decomposition precludes this method for most HOIPs. In this work, we describe the first mechanochemically-induced crystal-glass transformation of HOIPs as a rapid, green and efficient approach for producing glasses. The amorphous phase was formed from the crystalline phase within 10 minutes of ball-milling, and exhibited glass transition behaviour as evidenced by thermal analysis techniques. Time-resolved in situ ball-milling with synchrotron powder diffraction was employed to study the microstructural evolution of amorphisation, which showed that the crystallite size reaches a comminution limit before the amorphisation process is complete, indicating that energy may be further accumulated as crystal defects. Total scattering experiments revealed the limited short-range order of amorphous HOIPs, and their optical properties were studied by ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy.

  View details for DOI 10.1039/d4sc00905c

  View details for PubMedID 38756817

  View details for PubMedCentralID PMC11095504

• Jahn-Teller Distortions and Phase Transitions in LiNiO2: Insights from Ab Initio Molecular Dynamics and Variable-Temperature X-ray Diffraction. Chemistry of materials : a publication of the American Chemical Society Genreith-Schriever, A. R., Alexiu, A., Phillips, G. S., Coates, C. S., Nagle-Cocco, L. A., Bocarsly, J. D., Sayed, F. N., Dutton, S. E., Grey, C. P. 2024; 36 (5): 2289-2303

  Abstract

  The atomistic structure of lithium nickelate (LiNiO2), the parent compound of Ni-rich layered oxide cathodes for Li-ion batteries, continues to elude a comprehensive understanding. The common consensus is that the material exhibits local Jahn-Teller distortions that dynamically reorient, resulting in a time-averaged undistorted R3̅m structure. Through a combination of ab initio molecular dynamics (AIMD) simulations and variable-temperature X-ray diffraction (VT-XRD), we explore Jahn-Teller distortions in LiNiO2 as a function of temperature. Static Jahn-Teller distortions are observed at low temperatures (T < 250 K) via AIMD simulations, followed by a broad phase transition that occurs between 250 and 350 K, leading to a highly dynamic, displacive phase at high temperatures (T > 350 K), which does not show the four short and two long bonds characteristic of local Jahn-Teller distortions. These transitions are followed in the AIMD simulations via abrupt changes in the calculated pair distribution function and the bond-length distortion index and in X-ray diffraction via the monoclinic lattice parameter ratio, amon/bmon, and δ angle, the fit quality of an R3̅m-based structural refinement, and a peak sharpening of the diffraction peaks on heating, consistent with the loss of distorted domains. Between 250 and 350 K, a mixed-phase regime is found via the AIMD simulations where distorted and undistorted domains coexist. The repeated change between the distorted and undistorted states in this mixed-phase regime allows the Jahn-Teller long axes to change direction. These pseudorotations of the Ni-O long axes are a side effect of the onset of the displacive phase transition. Antisite defects, involving Li ions in the Ni layer and Ni ions in the Li layer, are found to pin the undistorted domains at low temperatures, impeding cooperative ordering at a longer length scale.

  View details for DOI 10.1021/acs.chemmater.3c02413

  View details for PubMedID 38495898

  View details for PubMedCentralID PMC10938510

• Van Vleck analysis of angularly distorted octahedra using VanVleckCalculator. Journal of applied crystallography Nagle-Cocco, L. A., Dutton, S. E. 2024; 57 (Pt 1): 20-33

  Abstract

  Van Vleck modes describe all possible displacements of octahedrally coordinated ligands about a core atom. They are a useful analytical tool for analysing the distortion of octahedra, particularly for first-order Jahn-Teller distortions, but determination of the Van Vleck modes of an octahedron is complicated by the presence of angular distortion of the octahedron. This problem is most commonly resolved by calculating the bond distortion modes (Q 2, Q 3) along the bond axes of the octahedron, disregarding the angular distortion and losing information on the octahedral shear modes (Q 4, Q 5 and Q 6) in the process. In this paper, the validity of assuming bond lengths to be orthogonal in order to calculate the Van Vleck modes is discussed, and a method is described for calculating Van Vleck modes without disregarding the angular distortion. A Python package for doing this, VanVleckCalculator, is introduced and some examples of its use are given. Finally, it is shown that octahedral shear and angular distortion are often, but not always, correlated, and a parameter η is proposed as the shear fraction. It is demonstrated that η can be used to predict whether the values will be correlated when varying a tuning parameter such as temperature or pressure.

  View details for DOI 10.1107/S1600576723009925

  View details for PubMedID 38322718

  View details for PubMedCentralID PMC10840309

• Magnetic and Magnetocaloric Properties of the A2LnSbO6 Lanthanide Oxides on the Frustrated fcc Lattice. Inorganic chemistry Koskelo, E. C., Kelly, N. D., Nagle-Cocco, L. A., Bocarsly, J. D., Mukherjee, P., Liu, C., Zhang, Q., Dutton, S. E. 2023; 62 (26): 10317-10328

  Abstract

  Frustrated lanthanide oxides are promising candidates for cryogen-free magnetic refrigeration due to their suppressed ordering temperatures and high magnetic moments. While much attention has been paid to the garnet and pyrochlore lattices, the magnetocaloric effect in frustrated face-centered cubic (fcc) lattices remains relatively unexplored. We previously showed that the frustrated fcc double perovskite Ba2GdSbO6 is a top-performing magnetocaloric material (per mol Gd) because of its small nearest-neighbor interaction between spins. Here we investigate different tuning parameters to maximize the magnetocaloric effect in the family of fcc lanthanide oxides, A2LnSbO6 (A = {Ba2+, Sr2+} and Ln = {Nd3+, Tb3+, Gd3+, Ho3+, Dy3+, Er3+}), including chemical pressure via the A site cation and the magnetic ground state via the lanthanide ion. Bulk magnetic measurements indicate a possible trend between magnetic short-range fluctuations and the field-temperature phase space of the magnetocaloric effect, determined by whether an ion is a Kramers or a non-Kramers ion. We report for the first time on the synthesis and magnetic characterization of the Ca2LnSbO6 series with tunable site disorder that can be used to control the deviations from Curie-Weiss behavior. Taken together, these results suggest fcc lanthanide oxides as tunable systems for magnetocaloric design.

  View details for DOI 10.1021/acs.inorgchem.3c01137

  View details for PubMedID 37326623

  View details for PubMedCentralID PMC10324300

• Deciphering the <i>In Situ</i> Surface Reconstruction of Supercapacitive Bimetallic Ni-Co Oxyphosphide during Electrochemical Activation Using Multivariate Statistical Analyses ACS APPLIED ENERGY MATERIALS Saleh, A. A., Sayed, D. M., Nagle-Cocco, L. V., Divitini, G., Ghanem, L. G., Ducati, C., Allam, N. K. 2022; 5 (6): 7661-7673

  View details for DOI 10.1021/acsaem.2c01122

  View details for Web of Science ID 000820371700001

• Pressure Tuning the Jahn-Teller Transition Temperature in NaNiO2. Inorganic chemistry Nagle-Cocco, L. A., Bull, C. L., Ridley, C. J., Dutton, S. E. 2022; 61 (10): 4312-4321

  Abstract

  NaNiO2 is a layered material consisting of alternating layers of NaO6 and Jahn-Teller-active NiO6 edge-sharing octahedra. At ambient pressure, it undergoes a broad phase transition from a monoclinic to rhombohedral structure between 465 and 495 K, associated with the loss of long-range orbital ordering. In this work, we present the results of a neutron powder diffraction study on powdered NaNiO2 as a function of pressure and temperature from ambient pressure to ∼5 GPa between 290 and 490 K. The 290 and 460 K isothermal compressions remained in the monoclinic phase up to the maximum pressures studied, whereas the 490 K isotherm was mixed-phase throughout. The unit-cell volume was fitted to a second-order Birch-Murnaghan equation of state, where B = 119.6(5) GPa at 290 K. We observe at 490 K that the fraction of the Jahn-Teller-distorted phase increases with pressure, from 67.8(6)% at 0.71(2) GPa to 80.2(9)% at 4.20(6) GPa. Using this observation, in conjunction with neutron diffraction measurements at 490 K on removing pressure from 5.46(9)  to 0.342(13) GPa, we show that the Jahn-Teller transition temperature increases with pressure. Our results are used to present a structural pressure-temperature phase diagram for NaNiO2. To the best of our knowledge, this is the first diffraction study of the effect of pressure on the Jahn-Teller transition temperature in materials with edge-sharing Jahn-Teller-distorted octahedra and the first variable-pressure study focusing on the Jahn-Teller distortion in a nickelate.

  View details for DOI 10.1021/acs.inorgchem.1c03345

  View details for PubMedID 35238545

  View details for PubMedCentralID PMC9098164