Defect Dynamics Research Articles

Orientation-dependent ductility and deformation mechanisms in body-centered cubic molybdenum nanocrystals

The knowledge regarding anisotropic mechanical behaviors in nanoscale body-centered cubic (bcc) metals remains obscure. Herein, we report the orientation-dependent ductility in bcc Mo nanocrystals (NCs), which exhibit poor ductility along [110] direction but possess relatively better ductility along the [001] and [112] orientations. The origin of different deformability can be traced down to the distinct deformation mechanisms: the unexpected crack nucleation and propagation induce premature fractures in [110]-oriented NCs; in contrast, deformation twinning could contribute to the enhanced ductility in [001]-oriented NCs; interestingly, we find the activation of multiple dislocation slips in [112]-oriented NCs with the highest ductility. Further molecular dynamics simulations provide deeper insights into the defect dynamics that are closely interlinked with experimental observations. Our findings advance the basic understanding of orientation-dependent mechanical properties and help to guide endeavors to architecture the microstructures of bcc metals with enhanced ductility.

Structural dynamics of Schottky and Frenkel defects in CeO2: a density-functional theory study

Cerium dioxide CeO2 (ceria) is an important material in catalysis and energy applications. The intrinsic Frenkel and Schottky defects can impact a wide range of material properties including the oxygen storage capacity, the redox cycle, and the ionic and thermal transport. Here, we study the impact of Frenkel and Schottky defects on the structural dynamics and thermal properties of ceria using density functional theory. The phonon contributions to the free energy are found to reduce the defect formation free energies at elevated temperature. The phonon dispersions of defective CeO2 show significant broadening of the main branches compared to stoichiometric ceria. Phonon modes associated with the defects are identifiable in the infrared spectra through characteristic shoulders on the main features of the stoichiometric fluorite structure. Finally, the presence of Frenkel and Schottky defects are also found to reduce the thermal conductivity by up to 88% compared to stoichiometric CeO2.

Hydrodynamic Enhancement of p-atic Defect Dynamics.

We investigate numerically and analytically the effects of hydrodynamics on the dynamics of topological defects in p-atic liquid crystals, i.e., two-dimensional liquid crystals with p-fold rotational symmetry. Importantly, we find that hydrodynamics fuels a generic passive self-propulsion mechanism for defects of winding number s=(p-1)/p and arbitrary p. Strikingly, we discover that hydrodynamics always accelerates the annihilation dynamics of pairs of ±1/p defects and that, contrary to expectations, this effect increases with p. Our Letter paves the way toward understanding cell intercalation and other remodeling events in epithelial layers.

O-147 Dynamics of palpable udder half defects in early lactation in non-dairy ewes

O-147 Dynamics of palpable udder half defects in early lactation in non-dairy ewes

Phase Transition and Dynamics of Defects in the Molecular Piezoelectric TMCM-MnCl3 and the Effect of Partial Substitutions of Mn

We present dielectric and anelastic spectroscopy measurements of the molecular piezoelectric TMCM-MnCl3 and TMCM-Mn0.95M0.05Cl3 (M = Cu, Fe, Ni; TMCM = trimethylchlorometylammonium), whose powders were pressed into discs and bars and deposited as films on Si by Matrix-Assisted Pulsed Laser Evaporation (MAPLE). As in other molecular ferroelectrics, the dielectric permittivity ϵ′ drops at the structural transition temperature TC, below which the number of directions that the polar TMCM molecules visit is reduced, with the formation of ferroelectric domains. Concomitantly, the Young’s modulus E starts increasing and the elastic energy loss has a step-like increase, attributable to the motion of the domain walls. Both the dielectric and elastic anomalies indicate the improper character of the ferroelectric transition, where the ordering of the molecular orientations is not driven by the cooperative interaction of their electric dipoles. Below room temperature, at least two thermally activated relaxation processes appear both in the dielectric and anelastic spectra, whose real and imaginary parts measured at several frequencies can be fit with the Havriliak–Negami formula. The microscopic parameters so-obtained indicate that they are due to point defects, and it is argued that they are Cl vacancies and their complexes with TMCM vacancies. The considerable width of these relaxation maxima is explained by the geometry of the hexagonal perovskite structure. The partial substitution of Mn with 5% Ni has little effect on the anelastic and dielectric spectra, while Cu and, especially, Fe cause a large enhancement of the losses attributed to domain wall relaxation, with substantial contributions also above TC. The condensation of water from the humidity in the powders compacted by cold pressing was observed and discussed. The piezoelectric activity of the films was assessed by PFM.

Impact of chemical short-range order on radiation damage in Fe-Ni-Cr alloys

Chemical short-range order (CSRO), as a nanoscale atomic feature, has been found to significantly alter material properties in various alloys. Here, we use Fe-Ni-Cr alloys to demonstrate how CSRO affects defect properties and radiation behavior, based on extensive molecular dynamics simulations. Statistically significant results are obtained as a function of dose for three CSRO levels. The random solution as an energetically unfavorable state (negative stacking fault energy) shows the strongest tendency to enable diffusion, while a high CSRO degree scenario generally reduces the effective defect diffusivity due to trapping effects, leading to distinct defect dynamics. Notably, in the high-CSRO scenario, interstitial clusters are Cr-rich and interstitial loops preferentially reside in/near the Cr-rich CSRO domains. Also, CSRO is dynamically evolving in a decreasing or increasing manner upon irradiation, reaching a steady-state value. These new understandings suggest the importance of incorporating the effect of CSRO in investigating radiation-driven microstructural evolution.

Dynamics of CSBD Healing after Implementation of Dentin and Xenogeneic Bone Biomaterial

Autologous dentin is frequently used in guided bone regeneration due to its osteoinductive properties, which come from its similarity to native bone. On the other hand, the xenogeneic bone biomaterial Cerabone® serves as a biocompatible, but hardly resorbed biomaterial. During bone healing, an inflammatory, vascular, and osteogenic response occurs in which cytokines such as tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF), and osteopontin (OPN) are released locally and systemically. The aim was to follow up the dynamics (on days 3, 7, 15, 21, and 30) of critical-sized bone defect (CSBD) healing after the implantation of bovine devitalized dentin, rat dentin, and xenogeneic bone biomaterial. For this purpose, histological and histomorphometric methods were employed. Additionally, serum concentrations of TNF-α, VEGF, and OPN were monitored in parallel to better understand the biomaterial-dependent systemic response in rats. At the last time interval, the results showed that the bone defect was bridged over in all three groups of biomaterials. The rat dentin group had the highest percentage of bone volume (BV/TV) and the least percentage of residual biomaterial (RB), which makes it the most optimal biomaterial for bone regeneration. Serum concentrations of the TNF-α, VEGF, and OPN refer to systemic response, which could be linked to intense bone remodeling between days 15 and 21 of the bone healing.

Anomalous temperature dependence of self-interstitial diffusivity in metallic lithium and sodium

Despite the abundance and importance of alkali metals for various applications, the behavior of point and dimensional defects in them has remained terra incognita. At the same time, the growing interest to high-capacity Li-metal batteries and the study of Li electrodeposition mechanisms dictates the need to investigate the defect dynamics. Here, we report the results of MD simulations of atomic motions in bulk Li and Na, including vacancy and interstitial (particularly <111>-crowdion) defect dynamics. Our main finding is an anomalous temperature dependence of the apparent diffusion coefficient for self-interstitial atoms (SIA), namely, the diffusivity decrease with the temperature rise. To uncover the underlying mechanism, we analyzed the interplay between 1D motions in terms of mean squared displacement (MSD) and 3D motions due to SIA rotations or switching. We found that the coefficient for 1D crowdion migration along the 〈111〉 axes is virtually temperature independent in case of both Li and Na. This implies linear temperature dependence of the drag coefficient γ, in contrast to other BCC metals. High rotation frequency reaching several THz at 300 K seems to drive the 1D diffusion into a semi-ballistic mode, therefore also affecting the temperature dependence of the apparent 3D diffusion coefficient. We believe that our results contribute to the atomistic understanding of low-barrier processes in a crystal lattice.

Defect self-propulsion in active nematic films with spatially varying activity.

We study the dynamics of topological defects in active nematic films with spatially varying activity and consider two set-ups: (i) a constant activity gradient and (ii) a sharp jump in activity. A constant gradient of extensile (contractile) activity endows the comet-like +1/2 defect with a finite vorticity that drives the defect to align its nose in the direction of decreasing (increasing) gradient. A constant gradient does not, however, affect the known self-propulsion of the +1/2 defect and has no effect on the -1/2 that remains a non-motile particle. A sharp jump in activity acts like a wall that traps the defects, affecting the translational and rotational motion of both charges. The +1/2 defect slows down as it approaches the interface and the net vorticity tends to reorient the defect polarization so that it becomes perpendicular to the interface. The -1/2 defect acquires a self-propulsion towards the activity interface, while the vorticity-induced active torque tends to align the defect to a preferred orientation. This effective attraction of the negative defects to the wall is consistent with the observation of an accumulation of negative topological charge at both active/passive interfaces and physical boundaries.

Sirtuins and redox signaling interplay in neurogenesis, neurodegenerative diseases, and neural cell reprogramming.

Since the discovery of Neural Stem Cells (NSCs) there are still mechanism to be clarified, such as the role of mitochondrial metabolism in the regulation of endogenous adult neurogenesis and its implication in neurodegeneration. Although stem cells require glycolysis to maintain their stemness, they can perform oxidative phosphorylation and it is becoming more and more evident that mitochondria are central players, not only for ATP production but also for neuronal differentiation's steps regulation, through their ability to handle cellular redox state, intracellular signaling, epigenetic state of the cell, as well as the gut microbiota-brain axis, upon dietary influences. In this scenario, the 8-oxoguanine DNA glycosylase (OGG1) repair system would link mitochondrial DNA integrity to the modulation of neural differentiation. On the other side, there is an increasing interest in NSCs generation, from induced pluripotent stem cells, as a clinical model for neurodegenerative diseases (NDs), although this methodology still presents several drawbacks, mainly related to the reprogramming process. Indeed, high levels of reactive oxygen species (ROS), associated with telomere shortening, genomic instability, and defective mitochondrial dynamics, lead to pluripotency limitation and reprogramming efficiency's reduction. Moreover, while a physiological or moderate ROS increase serves as a signaling mechanism, to activate differentiation and suppress self-renewal, excessive oxidative stress is a common feature of NDs and aging. This ROS-dependent regulatory effect might be modulated by newly identified ROS suppressors, including the NAD+-dependent deacetylase enzymes family called Sirtuins (SIRTs). Recently, the importance of subcellular localization of NAD synthesis has been coupled to different roles for NAD in chromatin stability, DNA repair, circadian rhythms, and longevity. SIRTs have been described as involved in the control of both telomere's chromatin state and expression of nuclear gene involved in the regulation of mitochondrial gene expression, as well as in several NDs and aging. SIRTs are ubiquitously expressed in the mammalian brain, where they play important roles. In this review we summarize the current knowledge on how SIRTs-dependent modulation of mitochondrial metabolism could impact on neurogenesis and neurodegeneration, focusing mainly on ROS function and their role in SIRTs-mediated cell reprogramming and telomere protection.

Molecular dynamics simulations of radiation response of LiAlO2 and LiAl5O8

We report the findings of a computational investigation of defect production and migration in two lithium aluminate ceramics: LiAlO2 and LiAl5O8. Although the first ceramic, LiAlO2 has been widely investigated computationally, especially via molecular dynamics (MD), there have been no MD studies done on LiAl5O8 up to date, due to the lack of interatomic potentials for this system. This work implemented an existing set of Li-Al-O coulombic and Buckingham potential parameters for the LiAl5O8 system from the literature, followed by validating it based on experimental values of density, crystallinity, bond lengths and melting point. The Li+ diffusion in the two ceramics was examined and was found to be one order of magnitude slower in LiAl5O8 (D0 = 3.17 × 10−11 m2/s) as compared to that in LiAlO2 (D0 = 4.02 × 10−10 m2/s) at 600 K. The lithium vacancy migration barrier of 4.15 eV in LiAl5O8 was more than three times that in LiAlO2 (1.31 eV) possibly due to stronger ordering in the Li-O6 octahedra of LiAl5O8 than in Li-O4 tetrahedra of LiAlO2. The Li displacement threshold energy (Ed) in LiAl5O8 was found to have a median value of 68 eV which is much higher than that in LiAlO2 (40 eV). The greater Ed for Li signifies a lower likelihood for defect formation and clustering and thus lower tendency for amorphization in LiAl5O8. The presented results show the difference in defect dynamics in the two ceramics that may help us understand the susceptibility of the two ceramics to amorphization caused by irradiation.

Radiation tolerance and defect dynamics of ALD-grown HfTiO x -based MOS capacitors

The study of radiation response and reliability of high-k dielectric materials plays a prominent role in Complementary Metal Oxide Semiconductor (CMOS) technology for device applications in nuclear and space electronics. In the present work, radiation effects on Atomic Layer Deposition (ALD)-grown Hafnium Titanium Oxide (HfTiO x )-based MOS capacitors have been investigated. HfTiO x thin films grown on Si substrates were irradiated with 60Co gamma radiation across a wide range of doses (100–3 Mrad). The defects in the pristine and gamma-irradiated thin films were examined by Photoluminescence spectroscopy. By using Poole-Frenkel tunnelling mechanisms, the effects of defects on the I–V characteristics of devices have been studied, as a function of radiation dose. Furthermore, the C–V measurements exhibit notable changes in the density of oxide and interface traps in the films. These devices survived gamma irradiation doses of up to 3 Mrad despite minor variations in their electrical properties. Hence, this work demonstrates the radiation tolerance and suitability of HfTiO x -based MOS capacitors for applications in radiation environments.

Structures, thermodynamics and dynamics of topological defects in Gay-Berne nematic liquid crystals.

Topological defects are a ubiquitous phenomenon across different physical systems. A better understanding of defects can be helpful in elucidating the physical behaviors of many real materials systems. In nematic liquid crystals, defects exhibit unique optical signatures and can segregate impurities, showing their promise as molecular carriers and nano-reactors. Continuum theory and simulations have been successfully applied to link static and dynamical behaviors of topological defects to the material constants of the underlying nematic. However, further evidence and molecular details are still lacking. Here we perform molecular dynamics simulations of Gay-Berne particles, a model nematic, to examine the molecular structures and dynamics of +1/2 defects in a thin-film nematic. Specifically, we measure the bend-to-splay ratio K3/K1 using two independent, indirect measurements, showing good agreement. Next, we study the annihilation event of a pair of ±1/2 defects, of which the trajectories are consistent with experiments and hydrodynamic simulations. We further examine the thermodynamics of defect annihilation in an NVE ensemble, leading us to correctly estimate the elastic modulus by using the energy conservation law. Finally, we explore effects of defect annihilation in regions of nonuniform temperature within these coarse-grained molecular models which cannot be analysed by existing continuum level simulations. We find that +1/2 defects tend to move toward hotter areas and their change of speed in a temperature gradient can be quantitatively understood through a term derived from the temperature dependence of the elastic modulus. As such, our work has provided molecular insights into structures and dynamics of topological defects, presented unique and accessible methods to measure elastic constants by inspecting defects, and proposed an alternative control parameter of defects using temperature gradient.

Radiation response of Y3Al5O12 and Nd3+-Y3Al5O12 to Swift heavy ions: insight into structural damage and defect dynamics.

Understanding the behavior of a material under irradiation is paramount to its application in the nuclear industry. The present work explores the radiation response of garnet Y3Al5O12 (YAG) and Nd3+-substituted Y3Al5O12 (Nd-YAG) under a 100 MeV Iodine beam at varying fluences to mimic the effect of fission fragments. This is relevant to the potential application of garnet as a host for minor actinide (MA) transmutation (Nd3+: surrogate for long-lived MA (Am3+, Np3+, Cm3+)). The un-irradiated and irradiated YAG and Nd-YAG samples were investigated by X-ray diffraction and Raman spectroscopy. Positron annihilation spectroscopy, thermal spike modelling and theoretical studies have been employed to understand the role of substitution and defect energetics in influencing this radiation response. Although both materials were not completely amorphized under the present irradiation conditions, a tremendous loss in crystallinity could be observed with increase in fluence, the damage being much more in Nd-YAG. Ion track radii of 2.17 nm and 2.91 nm were estimated for YAG and Nd-YAG respectively. Thermal-spike calculations show an increase in radiation-induced transient temperatures upon Nd-substitution that causes greater radiation damage in Nd-YAG. The enhancement in radiation-induced damage with increasing ion-fluence manifests in broadening and weakening of the Raman modes and XRD peaks. An increase in the average positron annihilation lifetime indicated the creation of oxygen vacancies. The defect formation energies of Y3Al5O12 have been theoretically estimated via density functional theory (DFT) and unfavorable energies required for creating cation pair anti-sites have been proposed as one of the possible reasons for the relatively poorer radiation response of YAG. The irradiation behavior of Y3Al5O12 has been compared with disordered fluorite (YSZ) and zirconate pyrochlores, which are well-researched ceramics for MA transmutation.

In situ studies on defect formation dynamics in flash-sintered TiO2.

Flash-sintered (FS) ceramics have shown promising mechanical deformability at room temperature compared to conventional sintered ceramics. One major contributing factor to plasticity is high-density defects, such as dislocations, stacking faults and point defects, resulted presumably from the high electrical field during flash sintering. However, such direct experiemtnal evidence for defect formation and evolution under the electric field remains lacking. Here we performed in situ biasing experiments in FS and conventionally sintered (CS) polycrystalline TiO2 in a transmission electron microscope (TEM) to compare the defect evolution dynamics. In situ TEM studies revealed the coalescence of point defects under the electrical field in both FS and CS TiO2 and the subsequent formation of stacking faults, which are often referred to as Wadsley defects. Surprisingly, under the electrical field, the average fault growth rate in the FS samples is 10 times as much as that in the CS TiO2. Furthermore, the Magnéli phase, a 3D oxygen-deficient phase formed by the aggregation of Wadsley defects, is observed in the FS samples, but not in the CS samples. The present study provides new insights into defect dynamics in FS ceramics.

Spontaneous flows and dynamics of full-integer topological defects in polar active matter.

Polar active matter of self-propelled particles sustain spontaneous flows through the full-integer topological defects. We study theoretically the incompressible flow profiles around ±1 defects induced by polar and dipolar active forces. We show that dipolar forces induce vortical flows around the +1 defect, while the flow around the -1 defect has an 8-fold rotational symmetry. The vortical flow changes its chirality near the +1 defect core in the absence of the friction with a substrate. We show analytically that the flow induced by polar active forces is vortical near the +1 defect and is 4-fold symmetric near the -1 defect, while it becomes uniform in the far-field. For a pair of oppositely charged defects, this polar flow contributes to a mutual interaction force that depends only on the orientation of the defect pair relative to the background polarization, and that enhances defect pair annihilation. This is in contradiction with the effect of dipolar active forces which decay inversely proportional with the defect separation distance. As such, our analyses reveals a long-ranged mechanism for the pairwise interaction between topological defects in polar active matter.

Active nematics with deformable particles.

The hydrodynamic theory of active nematics has been often used to describe the spatio-temporal dynamics of cell flows and motile topological defects within soft confluent tissues. Those theories, however, often rely on the assumption that tissues consist of cells with a fixed, anisotropic shape and do not resolve dynamical cell shape changes due to flow gradients. In this paper we extend the continuum theory of active nematics to include cell shape deformability. We find that circular cells in tissues must generate sufficient active stress to overcome an elastic barrier to deforming their shape in order to drive tissue-scale flows. Above this threshold the systems enter a dynamical steady-state with regions of elongated cells and strong flows coexisting with quiescent regions of isotropic cells.

Atomic structures and carrier dynamics of defects in a ZnGeP2 crystal

ZnGeP2 (ZGP) crystals have attracted tremendous attention for their applications as frequency conversion devices. Nevertheless, the existence of native point defects, including at the surface and in the bulk, lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage, limiting their applications. Here, native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and optical measurements. The atomic structures of the native point defects of the Zn vacancy, P vacancy, and Ge-Zn antisite were directly obtained through an HAADF-STEM, and proved by photoluminescence (PL) spectra at 77 K. The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy, and the decay lifetimes of 180.49, 346.73, and 322.82 ps are attributed to the donor Vp+ → valence band maximum (VBM) recombination, donor GeZn+ → VBM recombination, and donor–acceptor pair recombination of Vp+ → VZn-, respectively, which further confirms the assignment of the electron transitions. The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results. Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser, doing good to the ZGP crystal growth and device fabrication.

Broadband ultrafast photogenerated carrier dynamics induced by intrinsic defects in &lt;inline-formula&gt;&lt;tex-math id="Z-20231102113631"&gt;\begin{document}$\boldsymbol\beta$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20231173_Z-20231102113631.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20231173_Z-20231102113631.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

The ultra-wide bandgap semiconductor gallium oxide &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; with enhanced resistance to the irradiation and temperature is favorable for high-power and high-temperature optoelectronic devices. &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; also exhibits great potential applications in the field of integrated photonics because of its compatibility with the CMOS technique. However, a variety of intrinsic and extrinsic defects and trap states coexist in &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, including vacancies, interstitials, and impurity atoms. The defect-related carrier dynamics in &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; not only adversely affect the optical and electrical properties, but also directly limit the performance of &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; based devices. Therefore, a comprehensive understanding of the carrier transportation and relaxation dynamics induced by intrinsic defects is very important. Supercontinuum-probe spectroscopy can provide a fruitful information about the carrier relaxation processes in different recombination mechanisms, and thus becomes an effective way to study the defect dynamics. In this work, we study the dynamics of carrier trapping and recombination induced by intrinsic defects in pristine &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; crystal by using wavelength-tunable ultrafast transient absorption spectroscopy. The broadband absorption spectra induced by the intrinsic defects are strongly dependent on the polarization of pump pulse and probe pulse. Particularly, two absorption peaks induced by the two defect states can be extracted from the transient absorption spectra by subtracting the absorption transients under two probe polarizations. The observed defect-induced absorption features are attributed to the optical transitions from the valence band to the different charge states of the intrinsic defects (such as gallium vacancy). The data are well explained by a proposed carrier capture model based on multi-level energies. Moreover, the hole capture rate is found to be much greater than that of the electron, and the absorption cross-section of the defect state is at least 10 times larger than that of free carrier. Our findings not only clarify the relationship between intrinsic defects and photogenerated carrier dynamics, but also show the importance in the application of &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; crystals in ultrafast and broadband photonics.

Topological phases in nanoparticle monolayers: can crystalline, hexatic, and isotropic-fluid phases coexist in the same monolayer?

Topological phases are stable configurations of matter in 2-dimensions (2D) formed via spontaneous symmetry breaking. These play a crucial role in determining the system properties. Though a number of fundamental studies on topological phase transitions and topological defect dynamics have been conducted with model colloidal systems (typically microns in size), the same is lacking on nanoparticle monolayers (NPMLs, typically made of ligand-coated sub-ten nanometer particles). Here, we show that in an evaporation-driven self-assembly process, the three topological phases, namely crystalline, hexatic, and isotropic-fluid phases, can coexist within the same NPML. We associate this coexistence with the local variation in particle size, which can be described by a unique frequency parameter (p25), quantifying the fraction of NPs that has size deviation greater than or equal to 25% of the mean size (where the deviation,ζ is defined as ζ = ((|Size-mean|)/mean)). The p25-values for the three phases are distinctly different: crystalline arrangement occurs when p25 < ∼0.02, while a hexatic phase exists for 0.02 ≤ p25 ≤ 0.1. For p25 ≥ 0.1, the isotropic-fluid phase occurs. Following KTHNY-theory, we further numerically extrapolate the occurrence of each phase to the accumulated excess planar strain in the NPML due to the presence of various topological defects in the structures.