Local Lattice Distortion Research Articles

Local orthorhombic lattice distortions in the paramagnetic tetragonal phase of superconducting NaFe1\u2212xNixAs

Understanding the interplay between nematicity, magnetism and superconductivity is pivotal for elucidating the physics of iron-based superconductors. Here we use neutron scattering to probe magnetic and nematic orders throughout the phase diagram of NaFe1−xNixAs, finding that while both static antiferromagnetic and nematic orders compete with superconductivity, the onset temperatures for these two orders remain well separated approaching the putative quantum critical points. We uncover local orthorhombic distortions that persist well above the tetragonal-to-orthorhombic structural transition temperature Ts in underdoped samples and extend well into the overdoped regime that exhibits neither magnetic nor structural phase transitions. These unexpected local orthorhombic distortions display Curie–Weiss temperature dependence and become suppressed below the superconducting transition temperature Tc, suggesting that they result from the large nematic susceptibility near optimal superconductivity. Our results account for observations of rotational symmetry breaking above Ts, and attest to the presence of significant nematic fluctuations near optimal superconductivity.

Compositional Dependence of Phase Selection in CoCrCu0.1FeMoNi-Based High-Entropy Alloys.

To study the effect of alloy composition on phase selection in the CoCrCu0.1FeMoNi high-entropy alloy (HEA), Mo was partially replaced by Co, Cr, Fe, and Ni. The microstructures and phase selection behaviors of the CoCrCu0.1FeMoNi HEA system were investigated. Dendritic, inter-dendritic, and eutectic microstructures were observed in the as-solidified HEAs. A simple face centered cubic (FCC) single-phase solid solution was obtained when the molar ratio of Fe, Co, and Ni was increased to 1.7 at the expense of Mo, indicating that Fe, Co, and Ni stabilized the FCC structure. The FCC structure was favored at the atomic radius ratio δ ≤ 2.8, valence electron concentration (VEC) ≥ 8.27, mixing entropy ΔS ≤ 13.037, local lattice distortion parameter α2 ≤ 0.0051, and ΔS/δ2 > 1.7. Mixed FCC + body centered cubic (BCC) structures occurred for 4.1 ≤ δ ≤ 4.3 and 7.71 ≤ VEC ≤ 7.86; FCC or/and BCC + intermetallic (IM) mixtures were favored at 2.8 ≤ δ ≤ 4.1 or δ > 4.3 and 7.39 < VEC ≤ 8.27. The IM phase is favored at electronegativity differences greater than 0.133. However, ΔS, α2, and ΔS/δ2 were inefficient in identifying the (FCC or/and BCC + IM)/(FCC + BCC) transition. Moreover, the mixing enthalpy cannot predict phase structures in this system.

Significant Structural Distortion in the Surface Region of 4H-SiC Induced by Thermal Oxidation and Recovered by Ar Annealing

The impacts of O2-oxidation and Ar-annealing processes on the local lattice distortion at surface of thermally-oxidized 4H-SiC (0001) were investigated by using in-plane XRD. The surface oxidation induces a significant increase of the lattice constant, whereas Ar-annealing results in a gradual relaxation of it. From the x-ray penetration depth dependence of the observed lattice constant, those anomalous changes of lattice constants occur only in the surface region of SiC substrate.

A comparison study of local lattice distortion in Ni80Pd20 binary alloy and FeCoNiCrPd high-entropy alloy

The effect of alloying Pd on the local lattice distortion (LLD) in the Ni and FeCoNiCr host matrixes is quantified by integrating local structure characterization and theoretical calculations. The local structure measurements reveal that the mean LLD in the FeCoNiCrPd high-entropy alloy (HEA) is twice as high as the Ni80Pd20 binary alloy though the FeCoNiCr base alloy has a negligible mean LLD. Density functional theory calculations unveil that the unexpected high mean LLD in FeCoNiCrPd is related to the high fluctuation of LLD in the FeCoNiCr matrix. These observations suggest a synergetic effect of chemical complexity on HEAs' mean LLD.

Full Color Luminescence Tuning in Bi3+/Eu3+-Doped LiCa3MgV3O12 Garnet Phosphors Based on Local Lattice Distortion and Multiple Energy Transfers.

In the pursuit of high-quality W-LED lighting, the precise control of emission color of phosphor materials is indispensable. Herein we report a series of single-composition Bi3+-doped LiCa3MgV3O12 garnet-structure phosphors, whose emission colors under n-UV excitation could be tuned from bluish green (480 nm) to yellow (562 nm) on the basis of local lattice distortion and VO43- → Bi3+ energy transfer. Furthermore, full-color luminescence tuning from bluish green to orangish red across the warm white light region was successfully achieved by designing VO43- → Bi3+ → Eu3+ energy transfers. More interestingly, the thermal stabilities of as-prepared samples were gradually enhanced through designing VO43-/Bi3+ → Eu3+ energy transfers. This work provides a new perspective for color tuning originating from simultaneous local lattice distortion and multiple energy transfers.

Effects of the Ba-substitution for Sr in the Bi-2201 phase of BiPb(Sr,La)2CuO6+δ

Polycrystalline samples of the Bi-2201 phase of BiPbSr1.15-xBaxLa0.85CuO6+δ have been prepared by the conventional solid-state reaction method. Through the Ba-substitution for Sr, the lattice becomes large while Tc decreases gradually. With increasing x(Ba), the hole concentration in the CuO2 plane decreases despite the increase in the number of excess oxygen. The suppression of the superconductivity may be due to the decrease in the hole concentration in the CuO2 plane and the increase in the local lattice-distortion caused by excess oxygen.

Evolution of local lattice distortion under irradiation in medium- and high-entropy alloys

A major challenge for future nuclear reactors is to design nuclear materials that can sustain extremely prolonged radiation damage. Local lattice distortion, considered as a core effect of high-entropy alloys (HEAs), can suppress the growth of radiation defects to control radiation performance. However, local lattice distortion in HEAs is rarely quantitatively measured. Here we employed total scattering technique to study the local structure of the face-centered cubic (fcc) equiatomic FeCoNiCr MEA, and FeCoNiCrMn and FeCoNiCrPd HEAs before and after ion irradiation. Their local lattice distortions were quantitatively evaluated based on the difference of lattice constant between the local structure and the average structure. We revealed that the mean local lattice distortion in the pristine samples varies in the following order: FeCoNiCr < FeCoNiCrMn < FeCoNiCrPd. Density functional theory (DFT) calculations further unveiled that the fluctuation of local distortions in FeCoNiCr and FeCoNiCrMn is less than 5%, whereas the highest bond-length fluctuation in FeCoNiCrPd can approach to 8%. Under irradiation the mean local lattice distortion in FeCoNiCr and FeCoNiCrMn evolves differently from FeCoNiCrPd by showing a relaxation behavior at low dose. And the impact of local lattice distortion on dislocation loops after a prolonged ion-irradiation was investigated by transmission electron microscope (TEM) and the underlying mechanism was discussed.

The Influence of Local Distortions on Proton Mobility in Acceptor Doped Perovskites

Optimizing proton conduction in solids remains the most promising solution for achieving intermediate temperature (∼750–1000 K) solid oxide fuel cell devices, and enabling selective membranes for H2 separation. Proton conduction, a thermally activated process, exhibits its highest rates in yttrium (Y) acceptor doped BaZrO3 at an optimal doping level of 20% Y. The presence of extended defects such as grain boundaries has typically generated a wide variability in reported conductivity values. This has hindered a fundamental mechanistic understanding of how (acceptor) doping levels correlate with the activation energy of protons to produce an optimal doping level for fast proton transport. While isolated dopants have been suggested as the primary source of proton trapping, our results indicate that it is the local dopant-density that matters. Here, we show that increasing the local dopant density promotes localized lattice distortions in the presence of point defects such as oxygen-vacancies or proton inters...

Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). The origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

Appearance of the octupole ordered phase IV in CexLa1−xB6

We investigated the physical properties of ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{B}}_{6}$ at $x\ensuremath{\sim}0.8$, below which the ${T}_{\ensuremath{\beta}}$-type antiferro-octupole (AFO) ordered phase IV appears as a result of the larger suppression rate of ${T}_{\mathrm{Q}}$ than ${T}_{\mathrm{N}}$ by La doping. The most important result is that while the peak of the specific heat at ${T}_{\mathrm{Q}}$ is rapidly suppressed and broadened by La doping, that at ${T}_{\mathrm{IV}}$ is sharp and large. This indicates that although the ${T}_{\ensuremath{\beta}}$-AFO order in the phase IV is robust against the local lattice distortion induced by La doping, the ${O}_{xy}$-type antiferroquadrupole (AFQ) ordered phase II is very weak. The ${T}_{xyz}$-AFO interaction is robust against La doping from the observation of the pronounced enhancement of ${T}_{\mathrm{Q}}$ even in a small $x$ region. Based on these La-doping effect of the multipole interactions, we carried out the mean-field calculation for the four-sublattice model to reproduce the magnetic phase diagrams of ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{B}}_{6}$. Based on the calculated results, we propose that the small splitting of the quartet is induced by La doping in phase I to explain the magnetic phase diagram for $x&lt;0.65$. We could obtain the calculated results roughly consistent with the experimental results, although there appear new problems. We classified the mechanisms of the four different types of the competition among the four interactions with roughly the same magnitude, which induce the interesting and complicated properties in ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{B}}_{6}$.

Investigation of Al2O3 Wet-Chemical Coatings on Cathode Materials of Lithium-Ion Batteries

Coating targeted particles using a wet-chemical method is a simple, effective, and easy-to-scale-up method to coat protective oxide layers. Previous studies have shown that wet coating Al2O3 on the surface of Li-ion battery cathode materials can effectively prevent their chemical and structural degradation during charging-discharging processes, and improve the lifetime of batteries. However, there are still a limited number of systematic investigations of the wet coating process for Al2O3 coatings on cathode materials. The selection of precursors, solvents, coating loadings, annealing conditions, and even the compatibility between the Al2O3 coating and the underlying cathode material, are synthetic variables that can change the interfacial structure and electrochemical performance of the coated cathode. In this work, we used the wet-chemical method to synthesize a series of Al2O3-coated LiNixMnyCo1-x-yO2 (NMC) particles, with various precursor-solvent combinations, Al2O3 loadings, annealing conditions, and cathode compositions. Using nuclear magnetic resonance, electron microscopy and high-resolution X-ray diffraction techniques, we have shown that the structural and chemical evolutions of the surface coatings are highly dependent on annealing temperatures, cathode compositions and precursor-solvent combinations. Higher annealing temperature lead to a more homogeneous, smoother, and conformal coating on cathode materials with the formation of LiAlO2 phase. Organic solvents in place of water also lead to a more evenly and strongly bonded coatings, particularly under low-temperature treatment. We have also found that the crystallization temperature of the coating layers is precursor dependent. In addition, we have discovered that decreasing Mn content facilitates the diffusion of surface aluminum into the bulk in samples that have undergone high-temperature annealing. This facilitates a transfer of aluminum cations from the surface coating to become a bulk dopant. This is confirmed by local Al chemical environment evolution, local lattice distortion and surface morphology changes. Density functional theory calculations indicate that the incompatibility between Mn and Al could be the reason of the composition dependence of surface Al insertion. Finally, we demonstrate that the diffusion of Al into the bulk, the low temperature treatment, and the aqueous coating process lead to poor cyclability and low capacity in charging-discharging process, indicating the importance of the optimized wet coating protocols and coating-cathode compatibility to the electrochemical performance of coated cathodes. This work is important to the development of better coating methods for the next generation cathode materials in Li-ion batteries.

(Invited) Photo- and Cathodo-Luminescence of InAsxP(1-x)/InP Quantum Well Structures Under the Effects of Low-Energy Ion Bombardment

We investigate photo-luminescence (PL) and cathodo-luminescence (CL) spectra of InAsP/InP quantum well (QW) structures under exposure to low energy ions, and more generally to the particles generated in a plasma reactor typically used for etching such materials. The samples contain QWs of constant thickness (7 to 8 nm) and graded As/P concentration such that each QW produces, at low temperature, a PL line at a well-defined and resolved energy. Adjusting the depth of the QWs below the sample surface, the PL/CL of these QWs is thus the signature of the depth-dependent interaction with the ions and particles from the plasma. We have exposed our QW structures to different kinds of plasmas, containing variable mixtures of halogen-based molecules / hydrocarbons / nitrogen and Ar. Previous studies [1], in particular based on a similar approach of using the QW as an internal probe of the ion – material interaction, have shown that atomic ions with energies in the range of 100 to a few 100’s eV penetrate III-V materials (like GaAs or InP) through a channeling process [2], even if their direction of impingement is not favorable for channeling. The angular dispersion is in general sufficient to produce channeling. The ions channel a certain distance into the crystal, and then stop due to de-channeling mechanisms. As a consequence, a quenching of the PL for the QWs in the region where the de-channeling occurred takes place. We extended the analysis looking not only at the intensity of the PL lines, but also at their spectral characteristics upon exposure to the ion fluxes. Fig. 1 illustrates a selection of the effects that we were able to identify and explain [3]. On fig. 1-a, a sample was exposed to the particles flux from a plasma discharge in SiCl4/H2/Ar. Under the conditions of this plasma discharge, etching actually occurs at a rate ≈ 250-300 nm/min., and we had to be careful not to etch the whole QW structure immediately. Fig. 1-a shows that: - the signal for the two QWs at the lower wavelength seems to disappear. These QWs are the ones closest to the sample surface - the emission bands from the other QWs exhibit energy shifts Transmission electron microscopy and secondary ion mass spectrometry (SIMS) show that actually the two QWs closest to the top surface have not been etched. SIMS shows the penetration of Cl-species below the surface, which probably play a role in the quenching of the PL for these QWs The sample on fig. 1-a was undoped. On fig. 1-b, the same experiment is conducted for a sample with the same QW sequence as that of fig. 1-a, but n-type doped such that a large built-in electric field is created across the QWs region. One can see that this changes completely the shape of the PL lines. The reason for this change can be attributed to the quantum confined Stark effect (QCSE), as shown in [4]. Interestingly, as seen on fig. 1-b, the effect of the interaction with the etching ions is significantly more pronounced than for the undoped sample. We have shown that this is caused by a specific channeling interaction involving ions (probably Cl- ions) which strongly screen the QCSE. Using plasmas containing N2 (which effect is to reduce the etch rate), very significant blue shifts of the PL lines are seen (up to more than 7 nm). These were associated with the incorporation of N deep in the sample, occupying interstitial positions, thus creating local compressive lattice deformation that leads to the blue shifts [3]. All these effects will be discussed in the context of a model that we established to describe the modifications of the luminescence properties of the QW structures under the effect of low-energy ion bombardment. We will also describe experiments on samples where we take benefit of the plasma etching to define nanoscale structures and examine the spatial variation of the PL/CL spectra after interaction with the ion beams. [1] D. L. Green, E. L. Hu, P. M. Petroff, V. Liberman, M. Nooney, and R. Martin, J. Vac. Sci. Technol., B 11, 2249 (1993). [2] R. Germann, A. Forchel, M. Bresch, and H. P. Meier, J. Vac. Sci. Technol., B 7, 1475 (1989). [3] J.P. Landesman, J. Jiménez, C. Levallois, F. Pommereau, C. Frigeri, A. Torres, Y. Léger, A. Beck, and A. Rhallabi, J. Vac. Sci. Technol., A 34, 041304-1 (2016). [4] L. Viña, E. E. Mendez, W. I. Wang, L. L. Chang and L. Esaki, J. Phys. C: Solid State 20, 2803 (1987). Figure 1

Material-genome perspective towards tunable thermal expansion of rare-earth di-silicates

Optimization of thermal expansion coefficient (CTE) mismatch among constituent rare-earth silicate layers is a critical challenge for the optimal multilayer thermal/environmental barrier coating (T/EBC) architecture for SiCf/SiCm CMCs. In this study, thermal expansion properties for β-, γ- and δ-RE2Si2O7 polymorphs are investigated via DFT calculations. The interaction between rare-earth (RE) atoms and neighboring bridging oxygen (OB) atoms, as well as the structure of [O3SiOBSiO3] pyrosilicate units are the characteristic “gene” that controls the positive or negative contribution from low-frequency vibration patterns to the overall phonon anharmonicity, and eventually determine the significantly different CTE of RE2Si2O7 polymorphs. Inspired by the concept of “genome modification”, γ-(Dy0.15Y0.85)2Si2O7 solid solution is designed and synthesized, which shows notable enhancements of CTE as compared with γ-Y2Si2O7. Such tunable CTE could presumably be explained by doping-induced localized lattice distortion around [O3SiOBSiO3] pyrosilicate units, leading to switchable magnitude of negative contribution from low-frequency phonons to thermal expansion.

SrFe1−xMoxO2+δ: parasitic ferromagnetism in an infinite-layer iron oxide with defect structures induced by interlayer oxygen

The recent discovered compound SrFeO2 is an infinite-layer-structure iron oxide with unusual square-planar coordination of Fe2+ ions. In this study, SrFe1−xMoxO2+δ (x < 0.12) is obtained by crystal transformation from SrFe1−xMoxO3−δ perovskite via low-temperature (≤380 °C) topotactic reduction. The parasitic ferromagnetism of the compound and its relationship to the defect structures are investigated. It is found that substitution of high-valent Mo6+ for Fe2+ results in excess oxygen anions O2− inserted at the interlayer sites for charge compensation, which further causes large atomic displacements along the c-axis. Due to the robust but flexible Fe-O-Fe framework, the samples are well crystallized within the ab-plane, but are significantly poorer crystallized along the c-axis. Defect structures including local lattice distortions and edge dislocations responsible for the lowered crystallinity are observed by high resolution transmission electron microscopy. Both the magnetic measurements and electron spin resonance spectra provide the evidence of a parasitic ferromagnetism (FM). The week FM interaction originated from the imperfect antiferromagnetic (AFM) ordering could be ascribed to the introduction of uncompensated magnetic moments due to substitution of Mo6+ (S = 0) for Fe2+ (S = 2) and the canted/frustrated spins resulted from defect structures.

Unveiling the charge density wave inhomogeneity and pseudogap state in 1T-TiSe2

By using scanning tunneling microscopy (STM)/spectroscopy (STS), we systematically characterize the electronic structure of lightly doped 1T-TiSe2, and demonstrate the existence of the electronic inhomogeneity and the pseudogap state. It is found that the intercalation induced lattice distortion impacts the local band structure and reduce the size of the charge density wave (CDW) gap with the persisted 2 × 2 spatial modulation. On the other hand, the delocalized doping electrons promote the formation of pseudogap. Domination by either of the two effects results in the separation of two characteristic regions in real space, exhibiting rather different electronic structures. Further doping electrons to the surface confirms that the pseudogap may be the precursor for the superconducting gap. This study suggests that the competition of local lattice distortion and the delocalized doping effect contribute to the complicated relationship between charge density wave and superconductivity for intercalated 1T-TiSe2.

Phase separation and local lattice distortions analysis of charge-ordered manganese films La1-xCaxMnO3-δ by Raman spectroscopy

Polycrystalline films La1-xCaxMnO3-δ (LCMO) deposited on (001) MgO substrates for three different Ca concentrations (x = 0.67, 0.75, 0.85) were studied by Raman spectroscopy, X-ray diffraction and scanning electron microscope (SEM). Images of the surface and cross-section (edge) of samples of all compositions were obtained using SEM with high (up to 1 nm) spatial resolution. It was demonstrated that changes occur in the morphology and the formation of preferential orientation films x = 0.75, 0.85 relative to the substrate. It was founded that with an increase in the quantity of calcium there occurs a decrease in parameter pseudocubic unit cell. We have investigated the temperature (80K-350K) dependence of the Raman spectra of LCMO films. We have shown that Raman response of polycrystalline films below 150K corresponds to the microscopic coexistence of isostructural phases, with crystallographic symmetry Pnma. Detailed analysis of spectra allows to detect the occurrence of several different local lattice distortions: structural phases that have weak Jahn–Teller or/and spin crossover induced structural distortions with distorted octahedra Mn3+O6 and symmetric or nearly symmetric Mn4+O6 octahedra and the octahedral tilts in charge-ordered manganese films LCMO with x = 0.67, 0.75 at low temperature. Our results confirm the coexistence of charge–ordered antiferromagnetic state and ferromagnetic metallic phases with the competition between super-exchange and double-exchange interactions.

First-principles study of interaction between vacancies and nitrogen atoms in fcc iron

The interaction between vacancies and nitrogen atoms in fcc iron has been systematically studied by first-principles calculations. The interstitial N atoms bind strongly with vacancies into VnNm clusters, and each vacancy prefers only two N atoms that locate at the first nearest neighboring octahedral interstitial sites to the vacancy and align along the 〈1 0 0〉 directions. The number of N atoms is determined by the local lattice distortion evaluated by the expansion of atomic coordination polyhedrons with respect to the vacancy at the center. The most stable V1N2 cluster can be considered as a structural unit for the cluster development. Moreover, in larger VnNm clusters with relatively high stability, the vacancies aggregate at the center and the N atoms are around the vacancies. Then, the effect of N solute on radiation swelling depending on the N concentration is discussed from a perspective of the cluster formation. The radiation swelling increases with the N concentration because the existence of N atoms can promote the vacancy aggregation and, hence, the nucleation and growth of voids. However, as the concentration further increases, N atoms will saturate the surfaces of vacancy clusters to form barrier layers, which can hinder the combination of the VnNm clusters and the void formation.

Site dependent enhancement of magnetic anisotropy in 4d and 5d impurity doped α″-Fe16N2: A first principles study

Using the first principles method, we studied the electronic structure and magnetocrystalline anisotropy of site dependent 4d, 5d element doping in α″-Fe16N2. We found that different Fe sites contributed differently for magnetocrystalline anisotropy. For instance, on d-site doping, we obtained perpendicular magnetocrystalline anisotropy while the h-site doping resulted in an in-plane magnetocrystalline anisotropy in all the studied systems. The impurity doping induces local lattice distortions near the impurity site. However, the volume of the cell and total magnetic moment of the doped systems were not much affected. This local lattice distortion together with the spin-orbit coupling effect associated with heavy 4d, 5d element mainly contributed to enhancing the magnetocrystalline anisotropy. The enhancement of the magnetocrystalline anisotropy results in almost 15 to 67% enhancement of the coercivity for 4d element doping while we found 80 to 137% enhancement for 5d element doping. The maximum energy products were also enhanced compared to the pure α″-Fe16N2. The maximum enhancement was observed in Rh and Pt doped systems where the energy products were 119–120 MGOe. These results may suggest that substitutional doped α″-Fe16N2 system can be used as potential rare earth free permanent magnet.

Unified research of the EPR and optical spectral data for Cr3+-doped Lu3Al5O12 crystal

In this article, we apply a complete diagonalization (of energy matrix) method to simultaneously calculate the spin-Hamiltonian (or EPR) parameters (g factors g//, g⊥ and zero-field splitting D) and optical band positions (or crystal field energy levels) of Cr3+-doped Lu3Al5O12 (LuAG) crystal. The method is based on the two-spin-orbit-parameter model where besides the effects of spin-orbit parameter of central dn ion in the common crystal-field theory, those of ligand ions are contained. The calculated results indicate that by using only three adjustable parameters, the eight observed spectroscopic data (three EPR data and five optical bands) are reasonably explained. This suggests that this diagonalization method is effective and applicable in the unified calculation of EPR and optical spectral data for d3 ions in crystals. The local lattice distortion caused by the Cr3+ impurity in LuAG crystal is also estimated. The outcomes are discussed.

Long-term atomistic simulation of hydrogen absorption in palladium nanocubes using a diffusive molecular dynamics method

Understanding the transport of hydrogen within metallic nanomaterials is crucial for the advancement of energy storage and the mitigation of hydrogen embrittlement. Using nanosized palladium particles as a model, recent experimental studies have revealed several interesting phenomena that occur over long time periods. The time scale of these phenomena is beyond the capability of established atomistic models such as molecular dynamics. In this work, we present the application of a new approach, referred to as diffusive molecular dynamics (DMD), to the simulation of long-term diffusive mass transport at the atomic scale. Specifically, we simulate the absorption of hydrogen by palladium nanocubes with edge lengths in the range of 4 nm and 16 nm. We find that the absorption process is dominated by the initiation and propagation of an atomistically sharp α/β Pd-H phase boundary, with thickness in the range of 0.2 to 1.0 nm, which separates an α phase core from a β phase shell. The evolution of phase boundary and the resulting local lattice deformation are described in this paper in detail. The effects of size on both equilibrium and kinetic properties are also assessed.