Stability Of Grain Boundaries Research Articles

Atomistic Simulation Study of Grain Boundary Segregation and Grain Boundary Migration in Ni-Cr Alloys

Using Molecular Dynamics (MD) and Monte Carlo (MC) simulations, we studied the grain boundary (GB) segregation under different temperatures and Cr concentrations in Ni-Cr alloys with two distinct grain-boundary structures, i.e., Σ5(310)[010] and Σ101(200)[100]. Temperature plays a minor influence on Cr segregation for Σ5(310)[010] GB, but Cr segregation rapidly diminishes with elevating temperatures for Σ101(200)[100] GB. We also used the synthetic driving force and corresponding identification methods to investigate the effect of Cr solute segregation on grain boundary stability. All Σ5(310)[010] models have multi-stage grain boundary migration at 800 K. In the first stage, the grain boundary’s slow acceleration time is related to solute concentration. The migration temperature can influence this phenomenon. As temperatures rise, the duration of this slow acceleration phase diminishes. No similar phenomenon was observed in the process of the grain boundary movement of Σ101(200)[100]. The influence of solute concentration on grain boundary migration is complicated. The segregation concentration at the grain boundary cannot be regarded as the only factor affecting the migration of the grain boundary because the Cr atom on the grain boundary does not move with the grain boundary. This work will also discuss the grain boundary migration‘s relationship with lattice distortion and grain boundary atom diffusion. The results and findings of this study provide further insights into the segregation-increase GB stabilization of NC Ni-Cr alloys.

Maximizing the yield stress via synergistic optimization of grain sizes and solute concentrations in extremely fine nanograined metals: A molecular dynamics study

Molecular dynamics simulations are employed to investigate the grain boundary (GB)-segregation-induced strengthening and determine the maximal yield stress (MYS) in extremely fine nanograined Cu–Ag alloys, with variable grain sizes ranging from 5.2 to 17.9 nm alongside diverse solute concentrations. We discover that deformation mechanisms and yield stresses are adjustable through tailoring GB stability. The yield stress increases upon increasing solute concentration, up to a maximum (namely MYS) at a critical solute concentration for each grain size. The MYS shows a maximum of 3.70 to 3.72 GPa at a critical grain size of 7.3 to 10.3 nm. The strengthening and softening mechanisms related to GB segregation are uncovered, based on the model calculations and the dislocation analyses. Beyond the critical grain size, GB segregation suppresses GB-mediated processes while allowing dislocation activities, thereby causing a continuous strengthening. In contrast, below the critical grain size, the GBs, although being saturated, cannot withstand the resistance for GB deformation, which leads to a softening. This work presents a strategy to maximize the yield stress via synergistic optimization of grain sizes and solute concentrations, and provides insights into the design of ultrahigh-strength materials.

Grain boundary segregation behavior of Mo atoms in nanocrystalline Ni–Mo alloy

In this paper, molecular dynamics method was used to design the grain boundary (GB) segregation structure of solute atom Mo in nanocrystalline nickel, and the effect of the segregation structure on the migration and deformation mechanism of nanocrystalline Ni–Mo alloy boundaries was studied. The results indicate that the addition of solute atom Mo can cause segregation at GBs, and the yield strength and tensile strength of nanocrystalline Ni are significantly increased through solid solution strengthening. Mo atoms segregation result in an increase of the GB thickness and stability of the GB. In addition, by labeling GB atoms and tracking their diffusion trajectories, it was found that after adding Mo atoms, the probability of atomic diffusion at GBs decreased. This indicates that Mo atoms reduce GB energy and improve GB stability. Meanwhile, as the Mo content increases, the degree of atomic disorder increases, and the probability of GB migration decreases. This leads to the inability of grains to merge and inhibit their growth, effectively improving the mechanical properties of the material. As the strain increases, the number and length of dislocations increase, and a large amount of entanglement occurs at GBs. With the increase of Mo content, the number of dislocations decreases sharply, with Shockley dislocations having the highest number. Shockley dislocations interact with other dislocations and hinder their generation and movement, forming a more stable dislocation system structure and increasing the strength of the alloy. Our work focuses on observing the influence of GB segregation structure on the mechanical properties and deformation mechanism of nanocrystalline polycrystalline Ni–Mo alloys, establishing the mechanism of the influence of segregation structure on the stability and coarsening of nanocrystalline metal GBs, examining the influence of segregation structure on dislocation motion and GB migration process during deformation, and proposing positive research and development ideas and theoretical basis for designing nanocrystalline metal materials with excellent performance.

Atomic insights into the effect of rapid heating pretreatment on the mechanical stability of ⟨100⟩ symmetrical tilt GBs in nanocrystalline materials

Nanograined materials possess ultrahigh strength, while their processing and technological applications are constrained by inherent thermal and mechanical instability. Existing experiments show that the stability of Cu nanograins can be enhanced by performing a rapid heating pretreatment that reduces the grain boundary (GB) energy by changing the GB structure. The variation in the GB structure inevitably affects the migration mechanism of GBs. However, the effect of the pretreatment-induced variation in migration mechanisms on stability remains unclear. Here, the shear deformation of a series of ⟨100⟩ symmetrical tilt GBs after rapid heating pretreatment is systematically investigated by molecular dynamics simulations. The simulations of unheated GBs are also included for comparison. Our results show that the rapid heating pretreatment does not improve the mechanical stability of GBs with tilt angles larger than 36.87° but rather enhances the mechanical stability of those with tilt angles less than 36.87° by the transformation of migration behavior from the normal ⟨110⟩ mode to (i) a ⟨100⟩ mode; (ii) an inhomogeneous mixed one that reconciles the ⟨110⟩ and ⟨100⟩ modes; and (iii) an inhomogeneous ⟨110⟩ mode. The former leads to an increase in the critical shear stress that is required to initiate the migration, whereas the latter two result in a decrease in the migration distance. The variation in the GB migration mechanism is attributed to the change in the GB structure from an ordered kite structure to a disordered one. The research gives an atomic insight into the stabilizing mechanism of nanocrystalline materials with rapid heating pretreatment.

Screening and manipulation by segregation of dopants in grain boundary of Silicon carbide: First-principles calculations

The effect of segregation behavior of non-metallic dopants (H/He/O) and metallic dopants (Be/Al/Mg/Y) on the performance of grain boundary (GB) in SiC has been systematically investigated by first-principles calculations. Firstly, the GB energy and excess volume of different GBs have been studied to evaluate the stability of GB and the capacity to accommodate dopant atoms. The solution energies of dopant atoms greatly reduce in the GB region compared with those in the bulk, which makes the dopant atoms inside the grain tend to segregate and aggregate near the GB. The driving force of GB on dopant segregation generally decreases with the increase of distance from GB plane, and the preferential site of dopant is closely correlated with the atomic size of dopant. In addition, H and Y atom possesses the lowest segregation energy at the interstitial and substitutional site near the GB, respectively. Next, the segregation of single dopant induced the changes in the strength and stability of GB have been explored. It is found that non-metallic dopants have the significant embrittlement effects on GB strength. However, the segregation of most metallic dopants could strengthen the GB and Mg atom has the most significant strengthening effect on the GB. The stability of GB can be greatly improved by segregation of Al and Y dopants. Besides, the aggregation of H atoms has the obvious embrittlement effect on the GB. Furthermore, the co-segregation behavior of different dopants has also been explored. Be and Mg dopants have the most significant inhibition effect on the segregation of detrimental impurities H/He/O due to the repulsive interaction between dopant atoms. The present results provide a new insight into the effect of dopant segregation on GB properties and are expected to be a useful guidance for screening the chemical composition and manipulating the performance of SiC-based ceramics.

Thermodynamically Driven Tilt Grain Boundaries of Monolayer Crystals Using Catalytic Liquid Alloys.

We report a method to precisely control the atomic defects at grain boundaries (GBs) of monolayer MoS2 by vapor-liquid-solid (VLS) growth using sodium molybdate liquid alloys, which serve as growth catalysts to guide the formations of the thermodynamically most stable GB structure. The Mo-rich chemical environment of the alloys results in Mo-polar 5|7 defects with a yield exceeding 95%. The photoluminescence (PL) intensity of VLS-grown polycrystalline MoS2 films markedly exceeds that of the films, exhibiting abundant S 5|7 defects, which are kinetically driven by vapor-solid-solid growths. Density functional theory calculations indicate that the enhanced PL intensity is due to the suppression of nonradiative recombination of charged excitons with donor-type defects of adsorbed Na elements on S 5|7 defects. Catalytic liquid alloys can aid in determining a type of atomic defect even in various polycrystalline 2D films, which accordingly provides a technical clue to engineer their properties.

Effects of transition metal segregation on the thermodynamic stability and strength of Ni Σ11 [110](113) symmetrical tilt grain boundary

Precisely controlling grain boundary (GB) thermodynamic stability and strength is important for processing nanograined alloys. The segregation-induced stabilization and strengthening GB mechanisms of 20 transition metal elements in Ni Σ11 [110](113) STGB with low interfacial excess energy were clarified from first-principles total-energy calculations in this work. The results indicate that the segregation energy and GB energy are inversely related to the radius difference between TM and matrix Ni atoms. The segregation of 11 elements were identified to enable the Ni Σ11 [110](113) STGB to be stable according to Schuh criterion for GB stability. The electronic mechanism of GB stabilization through TM segregation is mainly due to the less anti-bonding states of Ni-X pairs than those of Ni–Ni pairs in unsegregated GB, from the analysis of crystal orbital Hamiltonian populations. The GB embrittlement resulted from TM segregation is mainly from the mechanical contribution caused by atomic size mismatch between segregation atom and matrix atom. The segregation caused GB strengthening comes from the chemical contribution, which is due to the fact that the segregation of X leads to the formation of stronger Ni-X covalent-like bonds instead of Ni–Ni metallic bonds. This work could provide better understanding on designing high-stable Ni nanograined alloys.

Revealing the structure-property relationships of amorphous carbon tribofilms on platinum-gold surfaces

Nanocrystalline metal alloys have shown great promise as electrical contact materials, given their mechanical and tribological properties. In particular, platinum-gold (Pt–Au) nanocrystalline alloys have demonstrated coefficients of friction as low as 0.01 and specific wear rates on the order of 10−9 mm3 N−1 m−1, largely due to the formation of carbon-based tribofilms at the sliding interfaces. In this study, we advance our understanding of the Pt–Au tribofilm structure-property relations and growth mechanisms via high-throughput and high-resolution measurements as a function of Pt–Au composition. As the solute content increased from 0 at. % to 10 at. % Au, cross-sectional and plan-view transmission electron microscopy demonstrated a decrease in average grain size d and an accompanied increase in grain boundary (GB) segregation. The decrease in d and increase in GB solute segregation translated to a decrease in modulus Er and an increase in hardness H as determined via nanoindentation; the Er trend was mainly described using a rule-of-mixtures approximation, whereas the H trend was ascribed to solid solution strengthening and GB stabilization. The steady state-friction μ and wear rate decreased with the addition of Au; low Au-content films showed substrate wear, while high Au-content films showed stable tribofilm growth in both macroscale and nanoscale friction tests. The carbon bonding configuration of the tribofilms was investigated by near-edge X-ray absorption fine structure spectroscopic analyses and found to be similar to that of hydrogenated amorphous carbon films. Altogether, the study provided insight into the mechanistic origins of the tribofilms, thus opening the door to tunable properties ranging from mitigation for electrical contacts to the creation of self-healing films for solid lubricants.

Tilt grain boundary stability in uranium dioxide and effect on xenon segregation

Grain boundaries (GBs) play a key role in the accumulation and release of xenon (Xe) in uranium dioxide (UO2). The stability and structure of tilt GBs with low sigma values in UO2 has been investigated by molecular statics/dynamics (MS/MD) simulations with three different empirical potentials. The atomistic modeling results confirm that Σ3 and Σ11 are more stable than both Σ5 and Σ9, consistent with previous work [J. Nucl. Mater. 517 (2019) 286]. In general, the higher distortion of atoms at a GB corresponds to a higher GB formation energy. Density functional theory (DFT+U) calculations indicate that a defective triangle-like pattern in the Σ5{310} is preferred rather than an oxygen-ring pattern. The energetics of Xe with or without vacancies at the most stable GBs have been studied by MS simulations. The incorporation energy profiles indicate that the Xe interstitial sites at the GBs are always energetically favorable in comparison to the bulk, while Xe incorporation in some Schottky defects (SDs) or uranium vacancy (VU) sites at the Σ5{210}, Σ5{310} and Σ9{221} boundaries are energetically unfavorable relative to the bulk. However, in general, interstitial Xe, Xe-SD, and Xe-VU complexes tend to segregate to the GBs. Notably, the symmetry degree of the distribution of excess atomic volume at a GB is correlated to the charge character of the GB. An asymmetric distribution of excess atomic volume results in the formation of electrostatic dipoles in GB systems, which significantly influences the segregation behavior of charged Xe-vacancy complexes at the GB. The segregation energy of Xe with or without vacancies is to some extent related to the GB excess volume.

Inhibiting creep in nanograined alloys with stable grain boundary networks.

Creep, the time-dependent deformation of materials stressed below the yield strength, is responsible for a great number of component failures at high temperatures. Because grain boundaries (GBs) in materials usually facilitate diffusional processes in creep, eliminating GBs is a primary approach to resisting high-temperature creep in metals, such as in single-crystal superalloy turbo blades. We report a different strategy to inhibiting creep by use of stable GB networks. Plastic deformation triggered structural relaxation of high-density GBs in nanograined single-phased nickel-cobalt-chromium alloys, forming networks of stable GBs interlocked with abundant twin boundaries. The stable GB networks effectively inhibit diffusional creep processes at high temperatures. We obtained an unprecedented creep resistance, with creep rates of ~10^-7 per second under gigapascal stress at 700°C (~61% melting point), outperforming that of conventional superalloys.

The effect of solute segregation on stability and strength of Cu symmetrical tilt grain boundaries from the first-principles study

Grain boundary (GB) stability and strength are two essential points for nanocrystalline materials. In this study, the effects and underlying mechanisms of segregation-induced GB stabilization and GB strengthening in various Cu GBs for selected 8 alloying elements (Mg, Ca, Cr, Ni, Zn, Zr, Ag and Sn) were investigated through first-principles total energy calculations. The segregation energy results show that all other elements excluding Ni can segregate to GB thus improving the GB stability. The segregation driving force is associated with the volume of Voronoi cell of solute, in the trend that increases along with the volume of Voronoi cell growth. The stabilizing mechanism should attribute to the decrease in the number of antibonding electrons. As to GB strength, the embrittling potency results show that Mg, Cr, Zr and Ag are enhancers in Σ5 [001](310) GB, while for Σ5 [001](210) and Σ11 [110](113) GBs, only Cr and Zr are enhancers. The embrittling potency is concerned with segregation energy and the volume of Voronoi cell of solute, in a trend that increases with the segregation energy decline and the volume of Voronoi cell growth. The enhancing mechanism lies in the formation of covalent-like bonds between solute and matrix atoms. Furthermore, by comparing the stabilizing and strengthening effectiveness of alloying elements in various Cu GBs. The trend that the worse the stability and strength of GBs, the better the stabilizing and strengthening effects of alloying elements were revealed.

Uncovering the softening mechanism and exploring the strengthening strategies in extremely fine nanograined metals: A molecular dynamics study

• Softening and strengthening in extremely fine nanograined metals are governed by grain boundary (GB) stability. • Atomic sliding in GB layer induces the softening while dislocation activity in grain interior plays the role of coordinator to fit the deformation dominated by GBs. • The solid solution exerts the negative strengthening (the softening) effect to the nanoscale metals. • The GB segregation gives rise to a notable improvement in strength, and this improvement can be further enhanced by optimizing solute concentration and GB excess. The strength of polycrystalline metals increases with decreasing grain size, following the classical Hall-Petch relationship. However, this relationship fails when softening occurs at very small grain sizes (typically less than 10 to 20 nm), which limits the development of ultrahigh-strength materials. In this work, using columnar-grained nanocrystalline Cu-Ag ‘samples’, molecular dynamics simulations were performed to investigate the softening mechanism and explore the strengthening strategies (e.g., formation of solid solution or grain boundary (GB) segregation) in extremely fine nanograined metals. Accordingly, the softening of pure metals is induced by atomic sliding in the GB layer, rather than dislocation activities in the grain interior, although both occur during deformation. The solid solution lowers the stacking fault energy and increases the GB energy, which leads to the softening of NC metals. GB segregation stabilizes GB structures, which causes a notable improvement in strength, and this improvement can be further enhanced by optimizing the solute concentration and GB excess. This work deepens the understanding of the softening mechanism due to atomic sliding in the GB layer and the strengthening mechanism arising from tailoring the GB stability of immiscible alloys and provides insights into the design of ultrahigh-strength materials.

Effects of Cu and Fe on cohesion and brittleness of grain boundary of tungsten

First principles calculation is performed to comparatively investigate the effects of Cu and Fe on energetics, cohesion properties, elastic properties, and fracture toughness of the ∑5(310)[001] grain boundary (GB) in body-centered cubic (BCC) W. It shows that both Cu and Fe have a tendency to segregate towards GB of BCC W and increase stability of GB with a lower GB energy. Calculations also indicate that Cu and Fe have a significant effect on decreasing the cohesion and increasing the brittleness of BCC W, which should be fundamentally attributed to lower bond energies of W–Cu and W–Fe bonds than the W–W bonds. The obtained results are interpreted and understood by bond energies and electronic structures, are consistent with existing experimental and theoretical observations, and would clarify the controversy about the effects of Cu and Fe on cohesion properties and brittleness of BCC W in the literature.

Zirconium-enhanced segregation tendency of solutes X and Zr-X co-segregation induced synergistic/antagonistic effects on Ni Σ5 [001](210) grain boundary

Manipulating grain boundary (GB) segregation of alloying elements has been established as an important pathway to optimize structural materials, due to the GB segregation induced changes in material properties, whereas solute interaction effects on GB segregation and properties remain far less developed. Here, the effects of solute interactions of Zr with X (X = Zr, Re, Ta and Cu) on the segregation behavior of solutes X at the Σ5 [001](210) GB of nickel-based superalloys, GB excess energy and fracture strength were investigated detailedly from first-principles calculations. It was found that the pre-segregation of Zr at the Ni GB not only enhances the segregation ability of subsequent solutes Zr, Ta and Cu, but also induces a GB segregation of Re that prefers grain interiors originally. Zr-Zr/Ta, Zr-Re and Zr-Cu co-segregations have synergistic potentiation, antagonistic and synergistic additive effects on improving the considered GB properties, respectively. Relative to the unsegregated GB, the Zr-Zr/Ta/Re co-segregations could improve the GB stability and fracture strength simultaneously, while the Zr-Cu co-segregation could only improve the GB stability. The co-segregation induced GB stabilizing/destabilizing and strengthening/weakening mechanisms were probed. These results would provide theoretical supports for the GB segregation engineering and quantitative composition design of high-performance nickel-based superalloys.

Quantitative experiments on the transition between linear to non-linear segregation of Ag in Cu bicrystals studied by radiotracer grain boundary diffusion

Abstract Non-linear segregation of Ag in Cu grain boundaries (GB) was quantitatively studied by radiotracer GB diffusion measurements on Cu bicrystals with non-special near Σ5 symmetrical [001] tilt boundaries. Bicrystals were used to guarantee a stable GB during the annealing avoiding in this way disturbing effects like GB motion etc. on the measured diffusion penetration profile. The 110mAg radioisotope with a well-defined specific activity was applied. This allowed to determine quantitatively the amount of Ag solute atoms in a section as a function of the penetration depth. The controlled variation of the total amount of diffusing Ag atoms along the Cu GB resulted in a fundamental change of the GB penetration profile shape from almost linear to strongly curved. The curvature of the penetration profiles was unambiguously shown to be caused by non-linear segregation of Ag in Cu GB. The full Ag segregation isotherm was calculated from the corresponding GB diffusion penetration profile.

Atomic configurations and energies of Mg symmetric tilt grain boundaries: ab initio local analysis

Mg alloys are highly expected for the wide application in the next-generation industry, while significant improvement of the plasticity of polycrystalline Mg alloys is crucial. For this purpose, it is essential to get insights into the atomic configurations, energetics, and mechanical responses of Mg grain boundaries (GBs). In this study, we investigated the overall features of atomic configurations and energies of and symmetric tilt GBs in hcp Mg by density-functional theory. We systematically constructed atomic models of coincidence-site lattice GBs by the arrangement of structural units in the full range of rotation angles. We observed that special GBs show clear cusps in both the GB-energy and excess-volume curves against the rotation angle. The reason of the stability/instability of each GB configuration was analyzed by ab initio local energy and local stress based on Bader partitioning. The features of local energies and stresses in Mg GBs are quite different from those in other materials with covalent or partial-covalent bonding nature. We observed substantial variations of local energies, local stresses and Bader charges of GB atoms, and charge inhomogeneity in a GB region, reflecting the structural disorder. Stable GBs are characterized by modest ranges of such variations and by moderate charge homogeneity. These results could be utilized in general to understand the interface stability and deformation mechanism of Mg and other simple metals.

The near-surface microstructural evolution and the influence of Si particles during nanoscratching of nanocrystalline Al

Molecular dynamics (MD) simulations are performed to study the near-surface deformation during nanoscratching on nanocrystalline Al. The influence of Si particle on wear behavior of nanocrystalline Al is also investigated by MD simulation. It is shown that the local deformation in nanocrystalline Al workpiece is associated with one or more mechanisms: (1) grain boundary (GB) migration, (2) GB sliding, (3) grain rotation, and (4) dislocations and deformation twin emitting from the indenter-workpiece interface and GBs. Moreover, the coarsening of Al grains is observed as the scratch proceeds. During grain coarsening, the low angle GB dissociates while the high angle GB migrates without dissociation. Interestingly, the GB motion is more active in nanocrystalline Al workpiece than that in Al/Si workpiece. The presence of Si particle changes the stress state of the adjacent Al grains, and therefore enhances the stability of GBs. Meanwhile, the specific wear rate in Al/Si workpiece is significant less than that in nanocrystalline Al workpiece, indicating that the Si particle enhances the wear resistance. In summary, this study sheds light on the interaction mechanism of second-phase and nanocrystalline matrix under sliding wear, which can provide theoretical support for the design of metal matrix composite with excellent wear resistance.

Grain boundary migration and deformation mechanism influenced by heterogeneous precipitate

AbstractUnderstanding the interaction between heterogeneous precipitates and grain boundaries (GBs) is of great significance for tailoring the stability and mechanical properties of nanograined materials. In this work, the nanoscale interaction between the cylindrical precipitate and the migrating GB is investigated by atomic simulation. The results show that the resistance for GB migration can be increased by decreasing the direction angle $$\alpha$$ α (the angle between the axis of the precipitate and the tilt axis of GB). For the larger precipitate, the influence of direction angle is more pronounced. With the increase in shear strain, the interaction between the specific precipitate and GB changes the material deformation mechanism from “GB migration” to “GB migration accompanied with activated dislocations or GB deformation,” which contributes to the softening of the material. By simultaneously tuning the direction angle and size of heterogeneous precipitates, the GB deformation can be strongly inhibited and the stability of GBs can be significantly improved.

Grain Boundaries in Minerals: Atomic Structure, Phase Transitions, and Effect on Strength of Polycrystals

Grain boundaries (GBs) and interfaces in polycrystalline materials are significant research subjects in the field of materials science. Despite a more than 50-year history of their study, there are still many open questions. The main challenge in studying interfacial structures is the extreme complexity of their experimental and theoretical observation and description. The presence of phase-like states at grain boundaries called complexions requires even more effort in their study. Here, we demonstrate the effect of grain boundaries on the properties of polycrystalline minerals on the example of the $\Sigma$5[310](001) grain boundary in periclase (MgO). Using the combination of extended evolutionary algorithm USPEX and modern machine-learning interatomic potentials, we explore the configuration space of the specified grain boundary and predict its possible phase-like states. In addition to the widely studied CSL-type structure, we found several stable GB complexions with various atomic densities at the boundary plane. Analysis of grain boundary excess volume of the structures revealed the successive stages of GB failure under the tensile applied in the normal direction of the boundary plane. Our results demonstrate that interfacial chemistry and structural diversity can be surprisingly rich even in seemingly simple and thoroughly investigated materials. The phenomena we observe here are not specific to MgO and should be general.

The Influence of Grain Structure in SEI on Lithium Diffusivity and Electrodeposition in Li-Metal Batteries

Lithium metal batteries (LMBs) are among the most promising candidates for high energy density energy storage technologies [1]. In order to make LMBs commercially competitive with the other mature energy storage devices, several aspect hindering LMBs’ widespread application shall be resolved. In particular, the growth of Li dendrites can cause the LMBs performance decrease as well as severe safety problems associated with the short circuit. In this regard, the solid electrolyte interface (SEI), a nanoscopic layer formed between the metal electrode and the liquid electrolyte, controls the Li delivery to the surface of the negative electrode, where Li electrodeposition and dendrites formation occur. Thus, the understanding of Li diffusivity (e.g., pathways, energetics, etc.) through the SEI could enable the development of strategies towards safe, robust and long-lasting LMBs. For that reason, in this contribution, we present the results of a combined ab initio Density Functional Theory (DFT) calculations to study Li diffusion across the SEI and an extended phase-field model (PFM) for Li migration and electrodeposition, that is a step forward toward better understanding of Li dendrites formation and growth. The present DFT calculations are performed using the VASP (Vienna Ab initio Simulation Package) code [2] with the plane wave basis sets and the projector augmented wave (PAW) [3] pseudo-potentials in the framework of Perdew-Burke-Ernzerhof sol (PBEsol) generalized gradient approximation (GGA) [4]. The migration barriers and diffusion coefficients are evaluated using the Nudged Elastic Band (NEB) method as implemented in VASP. To perform the NEB calculations, the minimum energy surfaces of each grain structure in SEI are first created, using a slab method. Then, the grain boundary (GB) structures are generated by forming stable interfaces between the minimum energy surfaces. After identifying the thermodynamically stable GBs, the lithium diffusion channels through them are identified, and the NEB calculations are performed. In the current study, we examine the migration barriers through the GBs of two major inorganic SEI grain structures such as Li2O and LiF. From the migration barriers, it could be observed that the diffusion through the GBs are almost two orders of magnitude faster than the compared diffusion coefficients through the bulk of the SEI structures. The evaluated diffusion coefficients and the free energies are then used to derive the thermodynamically consistent free energy density needed for the PFM model to simulate the filament growth and understand the distribution and evolution of stress fields during Li electrodeposition. The PFM [5] is developed employing MOOSE framework [6]. In the present work the effect of solid electrolyte interface (SEI) on the evolution of Li electrodeposits is captured by modeling the GB structures in SEI and diffusion through these GBs. The results from PFM reveal thatthe anisotropic nature of Li presence at the metal/SEI interface leads to uneven electrodeposition at the Li metal surface. In addition, an elastic deformation energy of the Li solid phase is included in the free energy functional of the PFM, which allows for monitoring the stress field evolution and its influence on Li filaments structure evolution. The present results also show that a significant stress is observed at the root of the Li electrodeposits and the triple junction between the GBs. This observation can guide the development of the experimental strategies for suppression of Li dendrites by lowering the stress field and also provide us more valuable information on the role of SEI as a transport medium, providing more scope for improvement on battery safety and performance.