Double Vacancy Research Articles

Scalable bottom-up synthesis of Co-Ni-doped graphene.

Introducing heteroatoms into graphene is a powerful strategy to modulate its catalytic, electronic, and magnetic properties. At variance with the cases of nitrogen (N)- and boron (B)-doped graphene, a scalable method for incorporating transition metal atoms in the carbon (C) mesh is currently lacking, limiting the applicative interest of model system studies. This work presents a during-growth synthesis enabling the incorporation of cobalt (Co) alongside nickel (Ni) atoms in graphene on a Ni(111) substrate. Single atoms are covalently stabilized within graphene double vacancies, with a Co load ranging from 0.07 to 0.22% relative to C atoms, controllable by synthesis parameters. Structural characterization involves variable-temperature scanning tunneling microscopy and ab initio calculations. The Co- and Ni-codoped layer is transferred onto a transmission electron microscopy grid, confirming stability through scanning transmission electron microscopy and electron energy loss spectroscopy. This method holds promise for applications in spintronics, gas sensing, electrochemistry and catalysis, and potential extension to graphene incorporation of similar metals.

Electronic and Magnetic Properties of Cobalt Clusters on Pristine and Divacancy Graphene

Using ab initio calculations we investigate the adsorption of Co atoms, dimers and small cobalt clusters of 5 and 13 atoms on pristine graphene and graphene with a double vacancy. We report the atomic, electronic, magnetic and energetic properties of these systems. Stable adsorption configurations tend to maximize the number of cobalt-carbon bonds. On graphene, the adsorption energy of the clusters is only about 0.4 to 1 eV, and the clusters are relatively mobile on graphene. Interestingly, for different adsorbed Co13 isomers on graphene it is found that they converge to the same atomic structure. On graphene with a divacancy, the Co clusters bind in the divacancy site and isomerisation also occurs for the Co5 cluster system as well as for Co13. Co atoms and clusters can be effectively immobilized on the divacancy with corresponding adsorption energy being significantly enhanced by about 5 to 7 eV. All clusters act as electron donors in the interaction with the graphene/divacancy systems, and the amount of electron charge transfer increases with cluster size. Finite magnetic moments occur for all systems, where upon adsorption, the magnetic moment of the isolated Co atom (3μB) is significantly reduced due to electron transfer and bonding, resulting in values varying from ≈0.9-2.2 μB per Co atom. For the pristine graphene substrate, the total induced magnetic moments on the carbon atoms are negligible, while on the divacancy system, they are of the order of 0.1-0.3 μB. The attractive physical properties of these hybrid systems could find applications in catalysis and materials science.

Vacancy Effect on the Luminescent and Water Responsive Properties of Vacancy-Ordered Double Perovskite Derivatives.

Vacancy-ordered perovskites and derivatives represent an important subclass of hybrid metal halides with promise in applications including light emitting devices and photovoltaics. Understanding the vacancy-property relationship is crucial for designing related task-specific materials, yet research in this field remains sporadic. For the first time, we use the Connolly surface to quantitatively calculate the volume of vacancy (V□, □=vacancy) in vacancy-ordered double perovskite derivatives (VDPDs). A relationship between void fraction and the structure, photoluminescent properties and humidity stability was established based on zero-dimensional (0-D) [N(alkyl)4]2Sb□Cl5□'-type VDPDs. Compared with the more commonly studied A2M(IV)X6□-type double perovskite (A=cation, M=metal ion, X=halide), [N(alkyl)4]2Sb□Cl5□' features double vacancy sites. Our results demonstrate an inverse relationship between the photoluminescent quantum yield and V□ in 0-D VDPDs. Additionally, structural transformation from A2SbCl5 to A3Sb2Cl9 was first reported, during which the novel 'gate-opening' gas adsorption phenomenon was observed in VDPDs for the first time, as evidenced by 'S'-shaped sorption isotherms for water vapor, indicating a cation-controlled water-vapor response behavior. A mixed-cation strategy was developed to modulate the humidity stability of VDPDs. Characterized by controllable water-responsive behavior and unique 'on-off-on' luminescent switching, A2M(III)□X5□'-type materials show great promise for multi-level information anti-counterfeiting applications.

Vacancy Effect on the Luminescent and Water Responsive Properties of Vacancy‐Ordered Double Perovskite Derivatives

AbstractVacancy‐ordered perovskites and derivatives represent an important subclass of hybrid metal halides with promise in applications including light emitting devices and photovoltaics. Understanding the vacancy‐property relationship is crucial for designing related task‐specific materials, yet research in this field remains sporadic. For the first time, we use the Connolly surface to quantitatively calculate the volume of vacancy (V□, □=vacancy) in vacancy‐ordered double perovskite derivatives (VDPDs). A relationship between void fraction and the structure, photoluminescent properties and humidity stability was established based on zero‐dimensional (0‐D) [N(alkyl)4]2Sb□Cl5□′‐type VDPDs. Compared with the more commonly studied A2M(IV)X6□‐type double perovskite (A=cation, M=metal ion, X=halide), [N(alkyl)4]2Sb□Cl5□′ features double vacancy sites. Our results demonstrate an inverse relationship between the photoluminescent quantum yield and V□ in 0‐D VDPDs. Additionally, structural transformation from A2SbCl5 to A3Sb2Cl9 was first reported, during which the novel ‘gate‐opening’ gas adsorption phenomenon was observed in VDPDs for the first time, as evidenced by ‘S’‐shaped sorption isotherms for water vapor, indicating a cation‐controlled water‐vapor response behavior. A mixed‐cation strategy was developed to modulate the humidity stability of VDPDs. Characterized by controllable water‐responsive behavior and unique ‘on‐off‐on’ luminescent switching, A2M(III)□X5□′‐type materials show great promise for multi‐level information anti‐counterfeiting applications.

Revealing the Synergistic Effect of Cation and Anion Vacancies on Enhanced Fenton-Like Reaction: The Electron Density Modulation of O 2p-Co 3d Bands.

Defect engineering is considered as a flexible and effective mean to improve the performance of Fenton-like reactions. Herein, a simple method is employed to synthesize Co3O4 catalysts with Co-O vacancy pairs (VP) for peroxymonosulfate (PMS) activation. Multi-scaled characterization, experimental, and simulation results jointly revealed that the cation vacancies-VCo contributed to enhanced conductivity and anion vacancies-VO provided a new active center for the 1O2 generation. Co3O4-VP can optimize the O 2p and Co 3d bands with the strong assistance of synergistic double vacancies to reduce the reaction energy barrier of the "PMS → Co(IV) = O → 1O2" pathway, ultimately triggering the stable transition of mechanism. Co3O4-VP catalysts with radical-nonradical collaborative mechanism achieve the synchronous improvement of activity and stability, and have good environmental robustness to favor water decontamination applications. This result highlights the possibility of utilizing anion and cation vacancy engineering strategies to rational design Co3O4-based materials widely used in catalytic reactions.

The synthesis of Bi2MoO6 with metallic and nonmetallic vacancies for degradation of LVF in visible light

Defect engineering advantages include regulating the band structure of photocatalytic materials, inhibiting the recombination of photoelectron-hole pairs, and promoting the conversion of photogenerated electrons into active radicals. In this paper, bismuth molybdate (Bi2MoO6) photocatalysts with double vacancies (VBi-O-BMO) were prepared by solvothermal and ionic eutectic solvent methods. EPR, TEM, and XPS results confirmed the successful construction of oxygen and bismuth vacancies on Bi2MoO6. The photocatalytic performance of the prepared catalysts was investigated by photodegradation of levofloxacin hydrochloride (LVF) under visible light. The double vacancies markedly enhanced the photocatalytic properties of Bi2MoO6, with the photodegradation rate of VBi-O-BMO reaching 88.36 % for 40 mg/L LVF within 60 min. Kinetic studies have demonstrated that the reaction rate constant of VBi-O-BMO can reach 0.0351 min−1, which is 3.2 times higher than that of bulk-BMO. This can be attributed to the favorable synergistic effect of oxygen and bismuth double vacancies. VO not only captures oxygen and electrons, facilitating the generation of superoxide radicals (O2−), but also elevates the conduction band position and boosts the reduction capability of Bi2MoO6. VBi not only captures photogenerated holes (h+) to directly impact LVF degradation, but also promotes interfacial charge transfer and inhibits the recombination of electron-hole pairs. Furthermore, the intermediates and degradation pathways of LVF photodegradation were surmised based on the LC-MS analysis. The reaction mechanism of LVF photodegradation by VBi-O-BMO was elucidated through the application of the free radical pathway. This study demonstrates a methodology for the creation of double vacancies in catalysts and the significant potential of VBi-O-BMO for the remediation of antibiotic residues in water under visible light.

Adjustable double cation vacancies MnSex/FeSex p-n heterojunction catalysts on improving multifunctional photocatalytic and photoelectrochemical performance

MnSex is a type of p-type semiconductor that combines with n-type FeSex in a one-step hydrothermal method to form a MnSex/FeSex p-n type heterojunction. The heterostructures showed good photocatalytic performance. The photocatalytic degradation rate constant of MFS3 was 0.01114 min−1, while that of MnSex was 0.00213 min−1. The photocatalytic degradation activity of MFS3 was 423 % higher than that of MnSex. Afterwards, the MnSex/FeSex catalyst was further soaked in ethylenediaminetetraacetic acid (EDTA) to form metal vacancies through metal complexation. A large number of pores can be seen in the SEM image of MFS3v catalyst, and Mn and Fe bimetallic vacancies can be seen in the TEM results. The signal of the electron paramagnetic spectrum is significantly enhanced, with a significant shift in its g value. The above results confirm the formation of Mn and Fe bimetallic vacancies in the catalyst. The two-hole heterojunction catalyst significantly improves its photochemical activity, and the photocurrent density of MFS3v at 0 V vs. RHE is −2.438 mA/cm2, 18.2 and 2.5 times that of the original MnSex and MnSex/FeSex heterojunction, respectively. Tests have confirmed that this double vacancy can increase the active sites and enhance the photoelectrochemical hydrogen production ability. This study proposes a method that combines heterojunctions and vacancies to achieve multifunctional catalysts.

Hollow ion atomic structure and X-ray emission in dense hot plasmas

Hollow ion X-ray emission is of great interest in high-energy-density research, since negligible opacity allows studies from the interior of very dense objects. In this paper, ionization potential depressions of the isoelectronic sequences for single and double K-shell vacancies are obtained from a pure ab initio multiconfiguration Hartree–Fock simulation including exact exchange terms and finite temperature dense plasma effects. It is demonstrated that the simultaneous representation of these ab initio data in the form of a map of hollow ion X-ray transition energies enables identification of important steps in the matter evolution and ionization dynamics. Mapping along the isoelectronic sequence as a function of the pumping energy of a X-ray free electron laser also enables visualization of the impact of ionization potential depression on the pathways of hollow ion formation.

Temperature and pressure driven functionalization of graphene with hydrogen and oxygen via ab initio phase diagrams

Functionalized graphene has numerous applications due to its remarkable and tunable physicochemical properties. However, precise control of functionalization remains challenging as direct connections between defect and functional group stability on graphene as a function of treatment conditions are missing. Here, a systematic study of graphene functionalization with hydrogen and oxygen is performed using a combination of density functional theory and ab initio phase diagrams. The interplay between carbon defects (e.g. vacancies, Stone-Wales, 555–777) and functionalization (e.g. R-H, R-H2, R-O, R-OH, and R-COOH) is examined. Generally, the process of functionalizing graphene led to significantly more stable carbon defects. By calculating Gibbs free formation energies with varying temperatures and partial pressures of H2 and H2O, ab initio phase diagrams were constructed. These diagrams revealed that the applied hydrogen and oxygen chemical potentials can be balanced during treatment to generate six distinct structures: R-H, R-O, R-OH, and R-COOH on the basal plane; and R-O and R-H2 on a double carbon vacancy. Through this systematic study, both the treatment conditions conducive to the formation of specific functional groups on graphene are pinpointed and a range of stable and metastable graphene-based structures with applications in various fields are identified.

Effects of vacancy defects and atomic doping on the electronic and magnetic properties of puckered penta-like PdPSe monolayer: an Ab initio study

The experimental knowledge of two-dimensional penta-like PdPSe monolayer is largely based on a recent publication (Liet al2021Adv. Mater. 2102541). Therefore, the aim of our research is consequently to explore the effect of vacancy defects and substitutional doping on the electronic properties of the novel penta-PdPSe monolayer by using first-principles calculations. Penta-like PdPSe is a semiconductor with an indirect bandgap of 1.40 eV. We show that Pd and Se vacancy defected structures are semiconductors with band gaps of 1.10 eV and 0.95 eV respectively. While P single vacancy and double vacancy defected structures are metals. The doping with Ag (at Pd site) and Si (at P site) convert the PdPSe to nonmagnetic metallic monolayer while the doping with Rh (at Pd site), Se (at P site) and As (at site Se) convert it to diluted magnetic semiconductors with the magnetic moment of 1µB. The doping with Pt (at the Pd site), As (at the P site), S and Te (at Se site) are indirect semiconductors with a bandgap of ∼1.2 eV. We undertook this theoretical study to inspire many experimentalists to focus on penta-like PdPSe monolayer growth incorporating different impurities and by defect engineering to tune the novel two dimensional materials (PdPSe) properties for the advanced nanoelectronic application.

Optoelectronic properties of a van der Waals heterostructure Black-Phosphorene/MoS[formula omitted] considering P-Atoms vacancy defects

We studied how the presence point defects could modify Black-Phosphorene/MoS2 van der Waals heterostructures’ optoelectronic properties. Specifically, we looked into the effects of various vacancy defects created by removing phosphorus atoms from Black-Phosphorene/MoS2 van der Waals heterostructures. We identified seven types of vacancies based on their formation energy and then analyzed their electronic and optical properties using density functional theory (DFT). Our findings revealed that double vacancies are the most likely structural defect and that mono vacancies and tetra vacancies result in a local spin magnetic moment of approximately 1.0 μB. These results emphasize the importance of considering spin polarization in these systems. We also observed that the band gap in the heterostructure is reduced compared to pristine phosphorene, indicating that the interaction with MoS2 plays a significant role in modulating the electronic and optical properties of the defective Black-Phosphorene/MoS2 van der Waals heterostructures.

Nitrogen doping retrofits the coordination environment of copper single-atom catalysts for deep CO2 reduction

The electrocatalytic CO2 reduction reaction (CO2RR) represents an effective way to address energy crises and environmental issues by converting CO2 into valuable chemicals. Single-atom catalysts (SACs) can achieve excellent catalytic activity in CO2RR. However, the study of CO2RR on SACs still poses significant challenges, especially in terms of controlling the selectivity towards the deep product such as CH4 and CH3OH. Herein, we employ density functional theory (DFT) calculations to investigate the CO2RR on Cu SAC supported on N-doped graphene (Cu-N/C) and explore the role of N dopants on the CO2RR performance. Compared to Cu SACs supported on N-doped defective graphene with double vacancy (Cu-N/C-DV), Cu SACs supported on N-doped defective graphene with single vacancy (Cu-N/C-SV) can effectively convert CO2 into the deeply reduced C1 products, including CH4 and CH3OH, thus further indicating that Cu-N/C-SV has a stronger interaction with ∗CO, which is conducive to the deep reduction of ∗CO. Increasing the coordination number of N atoms or the proximity of doping site to the Cu active site can effectively enhance the stability of catalyst and promote the adsorption of ∗CO on Cu-N/C-SV. However, this also increases the free energy of the formation of ∗CHO intermediate. The results suggest that CuC3-Nm, which contains a N atom in the second coordination shell (meta-position) of Cu SACs, has the best electrocatalytic performance of CO2RR in terms of both selectivity and catalytic activity, not only contributing to an in-depth understanding of the reaction mechanism of CO2RR on SACs but also providing insights into the design of SACs for efficient CO2RR.

W and Cu double cationic vacancies on S-scheme Bi2WO6/CuS heterojunction induced spin polarization and facilitated magnetic enhancement of photocatalytic activity toward levofloxacin degradation

In this research, the Bi2WO6/CuS heterojunctions (Vw-BWO/Cu1-xS) with Cu vacancies and W vacancies were fabricated via hydrothermal and post-etching methods towards levofloxacin (LEV) degradation. Multiple characterizations and tests verified the presence of W and Cu vacancies, and the Vw-BWO/Cu1-xS 10:1 heterojunction exhibited favorable optical properties. Density function theory (DFT) calculations revealed that W, Cu cation vacancies induced electron spin polarization on the Vw-BWO/Cu1-xS, facilitating carrier separation, and allowing more holes to be participated in photocatalytic reaction. Moreover, the presence of W, Cu vacancies could increase active sites, facilitating LEV absorption and activation. The Vw-BWO/Cu1-xS 10:1 composite achieved the highest LEV removal of 90.61 % within 60 min of light exposure, which was 1.24 times of the BWO. Notably, application of an external magnetic field (20 mT) to the Vw-BWO/Cu1-xS 10:1 could enhance photocatalytic degradation of LEV, which was 1.46 times of that without external magnetic field. Additionally, possible degradation routes of LEV and ecotoxicity of degradation intermediate products were determined. This study opens up a feasible approach for introduction of cationic vacancies and spin polarization on heterojunctions to improve photocatalytic activity.

The presence of Mo and O double vacancies in Bi2W0.25Mo0.75O6 solid solution promotes photogenerated charge separation and molecular oxygen activation for efficient removal of gaseous toluene under visible light

Enhancing indoor air quality and devising efficient technologies for the degradation of low-concentration volatile organic compounds (VOCs) represent pertinent topics in current research endeavors. In this study, a one-step hydrothermal method was employed to successfully synthesize a Bi2W0.25Mo0.75O6 solid solution photocatalyst featuring Mo and O double vacancies. The catalyst has excellent degradation effect on low concentration (30 ppm) gaseous toluene within 60 min of visible light irradiation, which can achieve 95.36 % in air atmosphere and 99.79 % in pure oxygen atmosphere. The incorporation of Mo vacancies in the solid solution photocatalyst proved instrumental in inhibiting carrier complexation, while O vacancies facilitated the activation of molecular oxygen. Concurrent Mo and O double vacancies extended the photo response range, expedited the transport of photogenerated charges, and diversified the reactive oxygen species pool, collectively enhancing toluene degradation. Hence, this study presents a compelling method for the fabrication of photocatalysts exhibiting visible light catalytic activity, with potential applications in the treatment and mitigation of real-world environmental pollution challenges under mild conditions.

Interaction of Titanium Atoms with the Surface of Perfect and Defective Carbon Nanotubes

The dispersion of metal atoms over the surface of 1D and 2D carbon systems is the most affordable way to control their properties, which are attractive for many applications in electronics, power engineering, and catalysis. In this work, the features of the interaction of titanium atoms with the surface of carbon nanotubes, caused by various structural defects on these surfaces, were studied by first-principles computer simulation based on the density functional theory. Nanotubes (7, 7) and (11, 0) with similar diameters (≈1 nm) but different types of conductivity, metallic and semiconductor, respectively, were chosen for the study. Three types of defects were studied: a single vacancy, a double vacancy, and a topological defect. Two possible orientations of each type of defect relative to the tube axis were considered. We mainly used the basis of atomic-like orbitals (the SIESTA package) and in some test calculations also the basis of plane waves (the VASP package). Computational experiments have shown that the binding energy of Ti atoms with a defect-free nanotube is always lower than with defective ones, regardless of the used approximation for the exchange-correlation functional (LDA or GGA). The binding energies predicted in the LDA approximation are noticeably higher than in the GGA approximation (up to ~15% for the (7, 7) tube and up to ~50% for the (11, 0) tube). The strongest coupling occurs when the titanium atom is adsorbed on a nanotube with a single vacancy. The resulting configuration can be considered as a defect in the substitution of one carbon by a titanium atom.

Influence of mono‐ and bi‐vacancy doped alkaline‐earth metals on the optoelectronic properties of monolayer defective state MoTe2: A first‐principles study

AbstractThe effects of single‐vacancy and double‐vacancy doping with alkaline‐earth metals on the stability, electronic structure, charge transfer, and optical properties of molybdenum ditelluride in the monolayer defective state (MoTe2) have been investigated using first‐principles methods. It is found that the structure of the molybdenum ditelluride system is more stable after double Te vacancies, with direct band‐gap to indirect band‐gap transitions occurring in single Te vacancies and Mo vacancies, and semiconductor to quasi‐metal transitions occurring in double Mo vacancies. The binding energy in the defect state system of molybdenum ditelluride after vacancy defects is always negative, and the structure remains stable. In this paper, the most stable double Te vacancy state was selected for substitutional doping with alkaline‐earth metals, and the Be atoms were doped with the largest amount of morphology, and Ca atoms were doped with the most pronounced decrease in band gap value. The direct band‐gap semiconductor is maintained after doping with Be atoms. Doping with Mg, Sr and Ba changes the band‐gap from direct to indirect. The double Te defect state MoTe2 doped with Ca atoms has a tendency to transition to a quasi‐metal. Regarding photoelectric properties, the system is blue‐shifted on both the absorption and reflection peaks.

Enhanced photocatalytic H2O2 production through synergistic double-vacancy engineering in Z-scheme TiO2-x/g-C3N4-x heterojunction

The photocatalytic synthesis of hydrogen peroxide (H2O2) is an environmentally benign and sustainable approach. In this study, we have synthesized a TiO2-x/g-C3N4-x(A-TxCNx) photocatalyst with a Z-scheme heterojunction by introducing oxygen and nitrogen double vacancies through a one-step reduction process. The optimized A-TxCNx catalyst exhibited a superior H2O2 yield of 1131.59 μmol L–1h−1 under visible light, which is 5.85 times greater than that of the A-TCN catalyst. This enhancement is ascribed to the synergistic effects of the oxygen vacancies (Ov) and nitrogen vacancies (Nv) defects, which amplify light absorption, facilitate electron-hole pair separation, and augment the number of active sites on the catalyst surface. Density functional theory (DFT) calculations and energy band analysis were employed to elucidate the photocatalytic mechanism of A-TxCNx, revealing that H2O2 synthesis predominantly occurs through two consecutive reactions, enabled by the catalyst’s unique electronic structure and defect configuration. This study not only validates the exceptional photocatalytic performance of A-TxCNx but also provides valuable insights for the design and optimization of future photocatalysts aimed at sustainable H2O2 production.

High-Valence Cu Induced by Photoelectric Reconstruction for Dynamically Stable Oxygen Evolution Sites.

Oxygen vacancies are generally considered to play a crucial role in the oxygen evolution reaction (OER). However, the generation of active sites created by oxygen vacancies is inevitably restricted by their condensation and elimination reactions. To overcome this limitation, here, we demonstrate a novel photoelectric reconstruction strategy to incorporate atomically dispersed Cu into ultrathin (about 2-3 molecular) amorphous oxyhydroxide (a-CuM, M = Co, Ni, Fe, or Zn), facilitating deprotonation of the reconstructed oxyhydroxide to generate high-valence Cu. The in situ XAFS results and first-principles calculations reveal that Cu atoms are stabilized at high valence during the OER process due to Jahn-Teller distortion, resulting in para-type double oxygen vacancies as dynamically stable catalytic sites. The optimal a-CuCo catalyst exhibits a record-high mass activity of 3404.7 A g-1 at an overpotential of 300 mV, superior to the benchmarking hydroxide and oxide catalysts. The developed photoelectric reconstruction strategy opens up a new pathway to construct in situ stable oxygen vacancies by high-valence Cu single sites, which extends the design rules for creating dynamically stable active sites.

First-principles study of lithium behavior in the ABA-stacking trilayer graphene with defects

To investigate the effect of defects on the Li embedding in graphene, we have studied the embedding and migration of Li in graphene with single-vacancy (SV), double-vacancy (DV), and Stone-Wales (SW) defects using the first-principles calculations. The results show that Li atom prefers to embed in regions with defect, and the presence of defect enhances the Li embedding in graphene. From the perspective of solution energy, Li embedded in the defect region of SV is the most stable, followed by the defect region of DV and SW. Migration results reveal that defects lead to an increase in the energy barrier for Li atom migration between layers and that Li is likely to be trapped in the defect region during migration. Open-circuit voltage and theoretical capacity calculations demonstrate that the lithium capacity of the ABA-stacking trilayer perfect graphene is 248 mAh/g. The lithium capacity diminishes to 165 mAh/g when a SW defect is present in the ABA-stacking trilayer graphene. In contrast, the lithium capacity increases to 270 mAh/g and 292 mAh/g when SV or DV defect is present in the ABA-stacking trilayer graphene, respectively. It is sufficient to show that graphene with low-density SW defect is unsuitable for application as electrode materials. Conversely, the low density of SV and DV defects can increase the lithium capacity of the ABA-stacking trilayer graphene at the same time, which will also lead to lithium deposition to some extent.

Phonon Transport in Defect-Laden Bilayer Janus PtSTe Studied Using Neural-Network Force Fields.

We explore the phonon transport properties of defect-laden bilayer PtSTe using equilibrium molecular dynamics simulations based on a neural-network force field. Defects prove very efficient at depressing the thermal conductivity of the structure, and flower defects have a particularly powerful effect, comparable to that of double vacancies. Furthermore, the conductivity of the structure with flower defects exhibits an unusual temperature dependence due to structural instability at high temperatures. We look into the distortion to normal modes around the defect by means of the projected phonon density of states and find diverse phenomena including localized modes and blue shifts.