Stable Defects Research Articles

P-Type conductivity mechanism and defect structure of nitrogen-doped LiNbO3 from first-principles calculations.

Most metal-doped lithium niobates (LiNbO3, LN) exhibit n-type conductivity. The absence of p-type conductive LiNbO3 limits its application. Based on the finding that p-type conductive LiNbO3 can be realized by doping with a non-metallic element N, we investigate the most stable defect configurations and formation energies of LiNbO3 doped with non-metal nitrogen (LN:N) by first-principles calculations. Nitrogen substitution, interstitial and quasi-substitution point defects in different sites and their effects were explored. The results show that N prefers to occupy the oxygen site with only little lattice distortion. Ab initio molecular dynamics (AIMD) simulations confirm the structural stability of an N ion occupying the O site. The charge-state transition level ε(0/-1) slightly above the valence band maximum (VBM) indicates that N point defects would contribute to p-type conductivity of LiNbO3. The analysis of the band structure reveals that the partially filled impurity levels can accommodate electrons that jump from valence bands and result in holes to become the main charge carriers. The calculation not only explains the occurrence of p-type conductivity in LN:N but also provides a simple and efficient way to discover p-type conductive candidates in numerous doped LiNbO3 crystals.

Importance of Many-Body Dispersion in the Stability of Vacancies and Antisites in Free-Standing Monolayer of MoS2 from First-Principles Approaches

Defects in MoS2 monolayer play a vital role in altering the electric and optical properties, which is a crucial factor in various semiconducting and optoelectronic devices. In the present work, we have investigated the thermodynamic stability of point defects in MoS2 monolayer by means of first-principles based density functional theory (DFT) and ab initio atomistic thermodynamics. We have considered three vacancies and five antisites in our system, viz. Mo vacancy (VMo ), SMo antisite, S2Mo antisite, S vacancy (VS ), MoS antisite, S2 vacancy (VS2 ), MoS2 antisite and 2MoS2 antisite. Our approach includes (i) the two-body van der Waals (vdW) interaction under Tkatchenko-Scheffler (TS) scheme and (ii) many-body dispersion (MBD) to account the effect of polarization on the defects’ stability. The MBD effect has posed a significant change in the pattern of stable defects. Hence, we report the stable defect states as observed by hybrid DFT with MBD as, V−2S , V−2Mo and S−2Mo in n-type MoS 2 monolayer, and V+2...

Composition dependent intrinsic defect structures in ASnO3 (A = Ca, Sr, Ba)

Perovskite stannates are promising semiconductors that are widely used in optoelectronic devices. Here, the composition dependent intrinsic point defects of stannate perovskites ASnO3 (A = Ca, Sr, Ba) are studied by first-principles calculations. The preferences of defects under stoichiometric and nonstoichiometric conditions are unsealed, meanwhile the charge states of each intrinsic defect varying with the change of electron Fermi energy are clarified. For stoichiometric BaSnO3 and SrSnO3, the Schottky defect complexes are predicted as the most stable defect structure, while the antisite defect complexes are the most stable one in CaSnO3. In nonstoichiometric ASnO3, excessive AO is beneficial to the formation of oxygen vacancies and A-Sn antisite defects in all ASnO3; while the Ca interstitial is another major defect existing in CaSnO3. In the case of SnO2 excess, the predominant defects are the Sn-A antisite defects and A vacancies. Since the functionality of these perovskite oxides is closely related to the types and concentrations of their point defects, the present results are expected to guide the future experiments to optimize the function of the perovskite oxides by tailoring the intrinsic defects through controlling the composition of AO and SnO2.

Defects around nanocolloids in nematic solvents simulated by Multi-particle Collision Dynamics

Colloids of nanometric size dispersed in a nematic environment are simulated using a hybrid algorithm that combines rules from Multi-particle Collision Dynamics and Molecular Dynamics. Coupling between flow and orientation fields is incorporated through the application of the Leslie–Ericksen theory for reorientation of slender rods under flow. It is found that Multi-particle Collision Dynamics sustains Saturn ring defects in the solvent when homeotropic anchoring on the colloids is considered. Changes on these topological structures induced by different anchoring strengths and spontaneous fluctuating flows are quantified. Stable defect structures around two close colloidal particles are observed that coincide with those obtained in experiments and alternative numerical techniques. Simulations of uniform nematic flow around the suspended colloid are conducted. It is found that Saturn rings are displaced along the stream direction. Large flows can separate the Saturn ring from the colloid, though the motion of the defect and the suspended particle reaches a steady state where disclinations are aligned with the streamlines.

In vivo perfusion of free skin flaps using extracorporeal membrane oxygenation

BackgroundThe vessel-depleted, irradiated, and frozen neck, as well as severe atherosclerosis of recipient vessels represent challenging problems in free flap transfer. Extracorporeal free flap perfusion theoretically allows free flap reconstructions in the absence of local donor vessels, but is associated with a number of technical issues. In this study, a novel technique is presented using a commercially available system for extracorporeal membrane oxygenation (ECMO), modified for small blood volumes. MethodsAfter preclinical testing, an ECMO system certified for lung support was used to establish blood flow through the flap's artery with oxygenation, decarboxylation and warming of diluted packed blood cells. Venous blood was allowed to flow passively into a separate container. Perfusion was performed for 15 min at intervals of 4 h over 4–6 days. ResultsFive patients with soft tissue defects requiring free flap reconstruction were included. Either primarily thinned anterolateral thigh (ALT) flaps (n = 3) or radial forearm flaps (n = 2) were used. We observed infection of the perfusate, with consequent subtotal flap loss, in one patient, complete epithelial loss in two patients, venous congestion in one case, and almost uneventful healing in the fifth patient. With conservative wound care and a split thickness skin graft in one case, stable wound coverage was achieved in all patients except one, who had secondary healing. None of the patients required a second flap for sufficient coverage. ConclusionsThe technique described is associated with the risks of infection, flap congestion, nutritive hypoperfusion, and consequent tissue loss. Nevertheless, stable defect closure seems to be achievable even in patients with depleted recipient vessels.

Structural evolution and the role of native defects in subnanometer MoS nanowires

We carried out first-principles calculations based on density functional theory aiming to understand the structural evolution along the stretching process and the impact of native defects in metallic subnanometer MoS nanowires (NWs). By pulling the pristine NWs quasistatically, we investigate the full structural evolution along the stretching process until the nanowire breaking point, obtaining a maximum applied stress (force) of $\ensuremath{\approx}18.9$ GPa (7.1 nN). On the other hand, since the existence of intrinsic defects is likely to occur in these samples, we show that under S-rich conditions a sulfur antisite is found to be the energetically most stable defect, and under Mo-rich conditions a sulfur vacancy has the lowest formation energy. Our results also reveal that these defects present local reconstruction that can be clearly identified by the simulated scanning tunneling microscopy images. Furthermore, through a detailed analysis of the electronic structure, we verify that with the exception of the Mo interstitial and S antisite, all defects preserve the metallic behavior of the MoS nanowires.

Interface defect engineering induced drastic sensing performance enhancement of W18O49@PANI nanowires for ammonia detection at room temperature

Room temperature gas sensor with high response and excellent stability has drawn much attention owing to its huge demand. Surface structure designs in a micro and macro scale provide lasting inspiration and a promising avenue for designing advanced functionalities using nanomaterials. Here, the W18O49@polyaniline (PANI) nanowires with rich and stable surface defects in its core-shell structure were constructed via facile hydrothermal process combined with plasma treatment. The results indicate that the surface oxygen vacancy defects induced by argon (Ar) or hydrogen (H) plasma can act as an electron acceptor to promote the PANI coating to generate more protons that react with the target Ammonia (NH3). Additionally, the coated PANI shell also can avoid the re-oxidate of the obtained oxygen vacancies, leading to a more stable and enhanced gas response of NH3 at room temperature. We found that the gas response of NH3 can be enhanced by increasing surface defect concentration, which can reach 50 and 25 at 100 ppm at room temperature with H and Ar plasma treat, respectively. Besides, a stable response-recovery performance in multiple cycles of 30 days and multiple cycles can achieve. Our results suggest that this interface designed W18O49@PANI is a potential ammonia gas sensor material.

Recent Research Trends in Point Defects in Copper Iodide Semiconductors

Copper iodide is a transparent p-type semiconductor that can be applied in thin-film transistors, transparent conductors, and light-emitting devices. Point defects affect the semiconductor properties of copper iodide. Therefore, many researchers have attempted to reveal the properties of point defects in copper iodide. A typical optical property related to point defects is photoluminescence (PL). PL peaks (430 nm and 700 nm) derived from defects have been reported for single-crystalline copper iodide. Density functional theory (DFT) studies reveal that the most stable defect species is the copper vacancy (VCu). These studies report that PL energies and defect species can be associated using experimental and DFT analyses. Researchers have also introduced defects into copper iodide single crystals or thin films artificially by controlling the annealing atmosphere and observed the relationship between the PL or absorption energy and Cu/I ratio. A comparison of this result with DFT results revealed that the photoactive defects were copper vacancies (VCu), iodine vacancies (VI), and iodine ions substituted at copper sites (ICu). Elucidation of the origin of fluorescence and coloration has enabled active control of optical properties via synthesis conditions. However, more drastic control of optical or electrical properties by doping is required for fabrication of actual devices. Some DFT studies on chalcogen doping have been reported; however, more theoretical and experimental studies are required.

A stable carbon host engineering surface defects for room-temperature liquid Na[sbnd]K anode

Alkali metal anode (Li, Na, K) are promising anodes for high-energy-density batteries because of high theoretical capacities and low redox potentials. While dendrite growth still restricts practical applications of alkali metal batteries. In contrast, liquid metal anode materials can avoid the problem of dendrite formation. But the poor wettability of liquid metal on most of hosts makes it difficult to assemble cell for the strong surface tension. Herein, we report a treated carbon cloth (denoted TCC) that can fast absorbs liquid NaK alloy at room temperature owing to the enhancing wettability by engineered surface defects of oxygenic groups and nanoscale cracks. When assembled in a symmetric cell with NaK alloy, it renders long cycle life over 1800 h and low voltage polarization below 300 mV compared with Na symmetric cell. When cycling with Na3V2(PO4)3 cathode as full cell, it also exhibits excellent capacity and capacity retention of 87.58% after 1000 cycles at 10 C.

A Failure to Start: Aborted Activation of CAR T Cells in Chronic Lymphocytic Leukemia

Introduction: Chronic Lymphocytic Leukemia (CLL) is a CD19+ B-cell malignancy that accounts for approximately 25% of adult leukemia diagnoses in the developed world. While conventional therapies have some efficacy, there are few curative therapeutic options and many patients ultimately progress to relapsed or refractory disease. CD19-targeting chimeric antigen receptor (CAR) T cell therapy has provided some hope, but induces complete remission in only 26% of patients. This suboptimal response rate is believed to be due to T cell dysfunction and immune-suppression by CLL cells, the mechanisms of which are poorly understood. Results: To understand the causes of CAR T cell dysfunction in CLL we investigated the defects that CLL cells induced in normal donor CD19-targeting CAR T cells. CAR T cells were repeatedly stimulated at 5-day intervals with either primary CLL cells from patients or a CD19-expressing control cell line (aAPC). Repeat stimulation of CAR T cells with aAPCs resulted in 5.36 ± .94 population doublings after three stimulations, whereas CLL cells only evoked 2.39 ± .92 population doublings. We performed phenotyping, proliferation analysis, and cytokine analysis of stimulated CAR T cells. CLL-stimulated T cells appeared un-activated, with low levels of PD-1, LAG3, and TIM3, low levels of cytokine production, and a high proportion of non-cycling cells as measured by Ki67 staining. We first hypothesized that CLL cells induce an altered epigenetic program that prevents effector function and is stabilized by successive stimulations. To test this, we stimulated CAR T cells with CLL cells or aAPCs as indicated in Fig. 1A. CLL-stimulated CAR T cells failed to proliferate or produce cytokines, but subsequent stimulation with aAPCs rescued these functions (Fig. 1B). Further, CLL-stimulated CAR T cells did not differentiate, suggesting that CLL cells do not induce stable defects but rather insufficiently activate CAR T cells (Fig. 1C). These cells also appeared un-activated as indicated by low levels of PD-1 and Ki67. We then used flow cytometry to assess expression of costimulatory and inhibitory molecules on the primary CLL samples. We found that the levels of co-stimulatory and adhesion molecules, namely CD80/CD86 and CD54/CD58 respectively were found at low frequencies, and where present were expressed at low levels. This suggested that one mechanism behind the lack of CAR T cell effector responses may be that a lack of co-stimulation prevents proper CAR T cell targeting of these cells. Towards this, we incubated CLL cells with a murine fibroblast line expressing CD40 ligand for 24 hours with IL-4 to activate the CLL cells. We found that this activation significantly increased expression of CD80, CD86, CD54, and CD58 on the CLL cells. We then used these cells to stimulate CAR T cells in our re-stimulation assay and found that CAR T cells were able to proliferate in response to these activated CLLs (Fig. 1D). In addition, CAR T cells stimulated with activated CLL cells formed more cell-to-cell conjugates than those stimulated with un-activated CLL cells. These data suggest not only that insufficient activation of CAR T cells may be responsible for the poor response rates to CAR T cell therapy in CLL, but also implicate a need for additional co-stimulation in this CAR T cell setting. Another contributing factor may be immune suppression by CLL cells. To determine if CLL cells are immune-suppressive, we used a co-culture assay to stimulate CAR T cells with aAPCs and CLL cells mixed at known ratios. Interestingly, all mixed cultures proliferated similarly, suggesting that CLL cells did not prevent T cell activation in the presence of a strong activation signal. We also found that CLL cells are responsive to IL-2, as addition of this cytokine to culture media prolongs survival of CLL cells out to 10 days depending on the dose. This suggests that CLL cells express a functional IL-2 receptor and may be taking up IL-2 from the culture media, further impairing T cell activation. In support of this, supplementing IL-2 into our CLL/CAR T cell co-cultures rescued T cell proliferative capacity. Taken together, these data suggest that T cell dysfunction in CLL is the result of insufficient activation rather than true functional defects. Disclosures June: Novartis: Research Funding; Tmunity: Other: scientific founder, for which he has founders stock but no income, Patents & Royalties. Melenhorst:National Institutes of Health: Research Funding; Parker Institute for Cancer Immunotherapy: Research Funding; Novartis: Research Funding, Speakers Bureau; IASO Biotherapeutics, Co: Consultancy; Simcere of America, Inc: Consultancy; Shanghai Unicar Therapy, Co: Consultancy; Colorado Clinical and Translational Sciences Institute: Membership on an entity's Board of Directors or advisory committees; Genentech: Speakers Bureau; Stand Up to Cancer: Research Funding; Incyte: Research Funding.

Cosmological evolution of semilocal string networks.

Semilocal strings-a particular limit of electroweak strings-are an interesting example of a stable non-topological defect whose properties resemble those of their topological cousins, the Abrikosov-Nielsen-Olesen vortices. There is, however, one important difference: a network of semilocal strings will contain segments. These are 'dumbbells' whose ends behave almost like global monopoles that are strongly attracted to one another. While closed loops of string will eventually shrink and disappear, the segments can either shrink or grow, and a cosmological network of semilocal strings will reach a scaling regime. We discuss attempts to find a 'thermodynamic' description of the cosmological evolution and scaling of a network of semilocal strings, by analogy with well-known descriptions for cosmic strings and for monopoles. We propose a model for the time evolution of an overall length scale and typical velocity for the network as well as for its segments, and some supporting (preliminary) numerical evidence. This article is part of a discussion meeting issue 'Topological avatars of new physics'.

Defects in Lead Halide Perovskite Nanocrystals: Analogies and (Many) Differences with the Bulk

Understanding the origin of defects in lead halide perovskite nanocrystals is paramount to attaining long-term structural stability and improved optical efficiency, key features for their successful implementation in optoelectronic devices. Unlike other studies, we explore the possible formation of trap states in explicit, nonperiodic CsPbBr3 nanocrystal models about 3 nm in size. Using density functional theory, we compute the defect formation energies of interstitial, vacancy, and antisite defects in different regions of the nanocrystal (center, surface center, and surface edge), demonstrating that the most stable defect position is found at the surface. We ascribe the high defect tolerance of CsPbBr3 nanocrystals to the fact that vacancies, i.e. the loss of surface ligands as ion pairs, are energetically difficult to form and only excessive stripping of surface ligands might be problematic, as their detachment leaves undercoordinated Br- on the crystal surface that only in this case translates into deep traps.

Theoretical Modeling of Defects, Dopants, and Diffusion in the Mineral Ilmenite

The iron titanium oxide ilmenite (FeTiO3) is a technologically and economically important mineral in the industrial preparation of titanium-based pigments and spintronic devices. In this study, atomistic simulation techniques based on classical pair potentials are used to examine the energetics of the intrinsic and extrinsic defects and diffusion of Fe2+ ions in FeTiO3. It is calculated that the cation anti-site (Fe‒Ti) cluster is the most dominant defect, suggesting that a small amount of cations exchange their positions, forming a disordered structure. The formation of Fe Frenkel is highly endoergic and calculated to be the second most stable defect process. The Fe2+ ions migrate in the ab plane with the activation energy of 0.52 eV, inferring fast ion diffusion. Mn2+ and Ge4+ ions are found to be the prominent isovalent dopants at the Fe and Ti site, respectively. The formation of additional Fe2+ ions and O vacancies was considered by substituting trivalent dopants (Al3+, Mn3+, Ga3+, Sc3+, In3+, Yb3+, Y3+, Ga3+, and La3+) at the Ti site. Though Ga3+ is found to be the candidate dopant, its solution enthalpy is >3 eV, suggesting that the formation is not significant at operating temperatures.

Microscopic mapping of dopant content and its link to the structural and thermal stability of yttria-stabilized zirconia polycrystals

The effect of yttria content on structural and thermal stability of zirconia in yttria-stabilized zirconia (YSZ) polycrystalline ceramics was systematically investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. Taking advantage of an experimentally retrieved linear dependence of Raman bandwidth on yttria content, Raman imaging was applied as an effective tool in examining the local yttrium distribution in YSZ ceramics and its relationship with environmentally driven polymorphic transformation. A significant variation of monoclinic fraction with yttria content and temperature was found and interpreted according to a newly proposed model, which takes into account the change in lattice hydroxyl and oxygen vacancies and the possible formation of stable defect complexes.

Building and exploring libraries of atomic defects in graphene: Scanning transmission electron and scanning tunneling microscopy study.

The presence and configurations of defects are primary components determining materials functionality. Their population and distribution are often nonergodic and dependent on synthesis history, and therefore rarely amenable to direct theoretical prediction. Here, dynamic electron beam-induced transformations in Si deposited on a graphene monolayer are used to create libraries of possible Si and carbon vacancy defects. Deep learning networks are developed for automated image analysis and recognition of the defects, creating a library of (meta) stable defect configurations. Density functional theory is used to estimate atomically resolved scanning tunneling microscopy (STM) signatures of the classified defects from the created library, allowing identification of several defect types across imaging platforms. This approach allows automatic creation of defect libraries in solids, exploring the metastable configurations always present in real materials, and correlative studies with other atomically resolved techniques, providing comprehensive insight into defect functionalities.

Synergetic effects of the interfacial dyadic structure on the interfacial charge transfer between surface-complex and TiO2

Surface-complex functional modification is a promising strategy in activating TiO2 for visible light harvesting. However, the fundamental nature of the interfacial microstructures between complex and TiO2, and how they affect the significant interfacial charge transfer process remain vague. In this work, a facile one-step visible-light-driven approach has been developed for the production of surface-complex and stable defects over TiO2 surface under normal ambient conditions. It is found that the photo-deposition of 2-naphthol on TiO2 can trigger a reconstruction of TiO2 surface to form a interfacial dyadic structure, which consists of conductive surface-complex and unique interfacial microstructures (Ti-O-C bonds and defects). defects. The interfacial defects (Ti3+ and oxygen vacancies) can be stabilized by the surface-complex coating, and introduce defective states in the band gap of TiO2. This unique interfacial dyadic structure can effectively promote the visible-light-driven photoelectric and photocatalytic performance. A corresponding mechanism is also proposed to elucidate the formation of this unique interfacial dyadic structure, and reveal its synergistic effect on the interfacial charge transfer behavior. This work contributes fundamentally to not only the mechanism studies, but also the rational design of novel and high-efficiency photocatalysts with high visible light harvesting.

Stability of non-metal dopants to tune the photo-absorption of TiO2 at realistic temperatures and oxygen partial pressures: A hybrid DFT study

TiO2 anatase is considered to play a significant importance in energy and environmental research. However, for developing artificial photosynthesis with TiO2, the major drawback is its large bandgap of 3.2 eV. Several non-metals have been used experimentally for extending the TiO2 photo-absorption to the visible region of the spectrum. It’s therefore of paramount importance to provide theoretical guidance to experiment about the kind of defects that are thermodynamically stable at a realistic condition (e.g. Temperature (T), oxygen partial pressure ({{boldsymbol{p}}}_{{{bf{O}}}_{{bf{2}}}}), doping). However, disentangling the relative stability of different types of defects (viz. substitution, interstitial, etc.) as a function of charge state and realistic T, {{boldsymbol{p}}}_{{{bf{O}}}_{{bf{2}}}} is quite challenging. We report here using state-of-the-art first-principles based methodologies, the stability and meta-stability of different non-metal dopants X (X = N, C, S, Se) at various charge states and realistic conditions. The ground state electronic structure is very accurately calculated via density functional theory with hybrid functionals, whereas the finite T and {{boldsymbol{p}}}_{{{bf{O}}}_{{bf{2}}}} effects are captured by ab initio atomistic thermodynamics under harmonic approximations. On comparing the defect formation energies at a given T and {{boldsymbol{p}}}_{{{bf{O}}}_{{bf{2}}}} (relevant to the experiment), we have found that Se interstitial defect (with two hole trapped) is energetically most favored in the p-type region, whereas N substitution (with one electron trapped) is the most abundant defect in the n-type region to provide visible region photo-absorption in TiO2. Our finding validates that the most stable defects in X doped TiO2 are not the neutral defects but the charged defects. The extra stability of {({bf{S}}{bf{e}}{bf{O}})}_{{bf{O}}}^{+{bf{2}}} is carefully analyzed by comparing the individual effect of bond-making/breaking and the charge carrier trapping energies.

Non-equilibrium steady structures of confined liquid crystals driven by a dynamic boundary

Steady structures originating from dynamic self-assembly have begun to show their advantages in new generation materials, and pose challenges to equilibrium self-assembly. In view of the important role of confinement in self-assembly, here, we propose a new type of confinement leading to dynamic steady structures, which opens a new window for the conventional confinement. In our model, we consider the self-assembly of ellipsoids in 2D circular confinement via the boundary performing periodically stretching and contracting oscillation. Langevin dynamics simulations reveal the achievement of non-equilibrium steady structures under appropriate boundary motions, which are novel smectic structures with stable topological defects. Different from the confinement with a static boundary, ellipsoids close to the boundary have variable orientations depending on the boundary motion. Order-order structural transitions, accompanied by the symmetry change and varied defect number, occur with the change of oscillating amplitude and/or frequency of the boundary. Slow and fast dynamics are distinguished according to whether structural rearrangements and energetic adjustment happen or not. The collective motion of confined ellipsoids, aroused by the work performed on the system, is the key factor determining both the structure and dynamics of the self-assembly. Our results not only achieve novel textures of circular confined liquid crystals, but also inspire us to reconsider the self-assembly within the living organisms.

First-Principles Investigation of the Structure and Properties of Au Nanoparticles Supported on ZnO

We present a first-principles investigation of the structure, stability, and reactivity of Au nanoparticles (NPs) supported on ZnO. The morphologies of supported Au NPs are predicted using the formation energy of Au surfaces and the adhesion energy between Au and the dominant ZnO surfaces exposed on ZnO tetrapods. We show how Zn interstitials (a stable intrinsic defect in ZnO) are attracted toward the Au/ZnO interface and in the presence of oxygen can lead to the encapsulation of Au by ZnO, an effect that is observed experimentally. We find that O2 molecules absorb preferentially at the perimeter of the NP in contact with the ZnO support. These results provide atomistic insight into the structure of ZnO-supported Au NPs with relevance to CO oxidation.

Investigations on structural, optical and ferromagnetic properties of Ni doped ZnO nanotwins

Ni doped ZnO nanotwin rods (nanotwins) have been fabricated by hydrothermal technique. Incorporation of Ni to the ZnO host lattice induces the morphological amendment which are being optimized and are investigated through scanning electron microscope. The diverse nature of interplanar spacing and orientation at the interface of ZnO nanotwins have been investigated through transmission electron microscope. Further, the local structure of Ni in the ZnO matrix has been studied through X-ray diffraction and X-ray photoelectron spectral analysis. Here, texture coefficient of (200) and photoluminescence spectra have been considered for the determination of defect states and the grain boundary mismatch. The existence of room temperature ferromagnetic property of the ZnO nanotwins has been manifested using magnetization hysteresis behavior. The optimized Ni ion concentration of 5% in ZnO nanorods yields nanotwins forming stable defects at Zn interstitial, oxygen vacancy and oxygen antisite helps to promote the ferromagnetic interaction to accomplish higher magnetic moment. Also, the presence of uncompensated surface spins in terms of charges on the surface of the nanoparticles have been analyzed through chronocoulometric analysis. The measured magnetic moment is 132 memu/g which is about 12 times greater than that of the pristine ZnO. In addition, the existence of room temperature ferromagnetism in ZnO nanotwins has been explained through bound magnetic polaron mechanism.