First-principles Density Functional Theory Research Articles

The first principle study on the hydrogen storage properties of monolayer and bilayer α-graphyne decorated by alkali metal atoms

Using the first-principles density functional theory, the hydrogen storage properties of monolayer and bilayer α-graphyne systems decorated by alkali metal are investigated. The results of band structure and density of state analysis indicate that alkali metal decoration enhances the chemical activity of the adsorption substrate, leading to increased H2 adsorption capacities for Li, Na and K decorated monolayer systems (15.0 wt.%, 14.5 wt.%, 10.7 wt.%, respectively). The combined action of interlayer force and decorated metal atoms results in higher H2 adsorption capacities for Li, Na and K decorated bilayer systems (17.7 wt.%, 16.9 wt.%, 13.0 wt.%, respectively), which means the bilayer graphyne structures enhance the storage capacities for decorated structures. Additionally, the Na decorated rhombus bilayer system demonstrates the highest adsorption density of H2 molecules between α-graphyne layers. Overall, alkali metal decorated monolayer and bilayer systems exhibit promising H2 adsorption potentials.

Atomic arrangement and mechanical properties of high-entropy nonoxide ceramics simulated via location preference-based disordered random structure

The cell structures and mechanical properties (i.e., hardness, Young's modulus, shear modulus, and Poisson's ratio) of (Hf0.2Zr0.2Ti0.2Nb0.2Ta0.2)C (HEC) and (Hf0.2Zr0.2Ti0.2Nb0.2Ta0.2)N (HEN) high-entropy ceramics were simulated by special quasi-random structure (SQS) and general random structure (GRS) with atomic occupation preference based on the first-principles density functional theory. The results show that compared to SQS, the cell structure constructed by GRS is more realistic, which is verified via scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy. The mechanical properties simulated by GRS were also determined by microhardness and dynamic elastic modulus testers. The hardness, Young's modulus，shear modulus and Poisson's ratio predicted by GRS are 23.07 GPa, 449.71 GPa, 183.28 and 0.227 for HEC and 22.96 GPa, 413.71 GPa, 162.47 and 0.241 for HEN, which are in a reasonable agreement with the measured results (i.e., 22.05 ± 0.32 GPa, 433 ± 12 GPa, 172 ± 18 GPa, 0.21 for HEC and 22.12 ± 0.13 GPa, 372 ± 23 GPa, 158 ± 11 GPa, 0.23 for HEN). This work can provide a promising reference for preparing high-entropy non-oxide ceramics via the prediction.

Adsorption and detection analysis of metal clusters (Pt3, Rh3) modified WTe2 monolayers to dissolved gases (CO, CO2, H2, C2H2) in transformer oil: A density functional theory study

Gas sensors are the key equipment in transformer fault online monitoring systems, and developing new and efficient gas sensing materials is an important prerequisite for breaking through existing monitoring performance. Herein, the first-principles density functional theory (DFT) is employed to study the adsorption and gas-sensing performance of two metal atomic clusters (Pt3 and Rh3) anchored on a WTe2 monolayer (C-WTe2) for four typical fault characteristic gases (CO, CO2, H2, and C2H2). These results suggest that four gases can stably bind to C-WTe2 and exist in the form of chemical adsorption due to the high adsorption energy. Also, Rh3-WTe2 exhibits high selectivity and repeatability towards CO and CO2 due to its strong response and fast recovery characteristics when used in resistive sensors; Pt3-WTe2 can detect and distinguish the four types of gases due to the significant and differentiated changes in work function when used in work function sensors. Therefore, both Pt3-WTe2 and Rh3-WTe2 monolayers are promising gas-sensing materials for the dissolved gases detection in oil. This investigation sheds light on devices of designing metal atomic cluster anchored WTe2-based gas sensor for improved transformer fault monitoring performances.

DFT formalism studies on the structural and electronic properties of hexagonal graphene quantum dot with B, N and Si substitutional impurities

The study of carbon-based nanostructured materials is a highly active research field, that has made significant progress in the study of twodimensional materials and nanotechnology. The interest in these materials is mainly attributed to the fascinating properties they exhibit, as seen in the case of graphene as a 2D material, as well as emergence on numerous novel 2D materials and their heterostructures. Additionally, there is important interest in systems such as 2D quantum dots. Therefore, this work focuses on the systematic study of graphene quantum dots of various sizes, all within the framework of first-principles density functional theory. We started with the simplest graphene quantum dot (GQD) structure, benzene (C6H6), which consist of six carbon atoms passivated with hydrogen atoms. We then increased its size by adding more aromatic rings, resulting in the following GQD configurations: C24H12, C54H18, C96H24, C150H30 and C216H36. We report the density of states (DOS) and the imaginary part of the dielectric function (ε2) for the system, analyzing both the pristine configuration and the effect of both single and double (boron, nitrogen and silicon, denoted as Sa). The double substitutional atom study was done considering random, ortho-, meta-, and para-director positions just for the C94H24Sa2 GQD. In general, we can conclude that as the GQD increases in size, the HOMO-LUMO energy decreases. Furthermore, it is observed that boron and nitrogen exhibit their expected n-, and p-type doping characteristics, but this differs between single and double Sa substitutions. Additionally, the imaginary part of the dielectric function is highly sensitive to the positions of single and double substitutional atoms, as well as the polarization of incident light. Therefore, we suggest that these differences can be used to clearly determinate the type of substitutional atoms and their positions from optical measurements.

First-principles study of electronic, mechanical, and optical properties of M3GaB2 (M = Ti, Hf) MAX phases

Integrating ceramic and metallic properties in MAX phases makes them highly desirable for diverse technological applications. In this study, through first-principles density functional theory (DFT), we investigated the physical properties of two new 312 MAX compounds, M3GaB2 (M = Ti, Hf). Chemical stability is confirmed via formation energy assessment, while mechanical stability is established by determining elastic stiffness constants. A thorough analysis of mechanical behaviors includes bulk modulus, shear modulus, Young's modulus, and hardness parameters. M3GaB2 demonstrates elastic constants and moduli closely aligned with other 312 carbides. Understanding the electronic band structure and density of states (DOS) sheds light on metallic properties, with anisotropy in electrical conductivity clarified through energy dispersion analysis. Investigation of photon interaction with titled compounds, including dielectric constants (real and imaginary parts), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function, has been carried out. The potential of M3GaB2 borides as a coating to reduce solar is evaluated based on the reflectivity spectra. These findings deepen our understanding of material properties and suggest diverse applications for M3GaB2 in various technological domains.

Deciphering reaction mechanism network of n-heptane dehydrocyclization over H-ZSM-5 zeolite

The dehydrocyclization of naphtha is a process of great significance in the petrochemical industry, as it enables the production of valuable aromatics. While experimental studies have demonstrated the catalytic activity of H-ZSM-5 zeolite in converting alkanes to aromatics, there is a notable absence of theoretical investigations into the reaction mechanisms involved in the dehydrocyclization of naphtha. Herein, the conversion of n-heptane to toluene over H-ZSM-5 zeolite was examined using first-principles density functional theory (DFT) calculations. The dehydrocyclization process of n-heptane involves several key steps, including dehydrogenation, isomerization, and cyclization. Specifically, the dehydrogenation of n-heptane produces 1-heptene, 2-heptene, and 3-heptene, which then undergo various dehydrocyclization pathways leading to the formation of toluene: (i) C1-C5 ring closure of 1-heptene; (ii) C1-C6 ring closure of 1-heptene; (iii) C2-C6 ring closure of 2-heptene; (iv) dehydrogenation of 3-heptene to heptadiene, with C1-C5 ring closure; and (v) dehydrogenation of 3-heptene to heptatriene, with C1-C6 ring closure, followed by sequential ring expansion and/or dehydrogenation to toluene. The DFT results indicate that the dehydrogenation steps are energetically demanding, with the conversion of n-heptane to toluene via 1-heptene identified as the most favorable cyclization route. This theoretical investigation provides valuable insights into the fundamental mechanisms underlying the dehydrocyclization of naphtha for the production of aromatics, with potential implications for the development of more efficient catalytic processes in the petrochemical industry.

Advancing tribological simulations of carbon-based lubricants with active learning and machine learning molecular dynamics

The need to move toward more sustainable lubricant materials has sparked an ever growing interest on the tribological performances of additives based on environmentally friendly molecules, such as carbon-based compounds, and green liquid media as aqueous solutions. The prediction of the solubility of the additives into the liquid and the tribochemistry of decomposition and polymerization of the additive molecules under harsh conditions is essential for understanding the atomistic mechanisms leading to the formation in situ of the carbon-based lubricious tribofilms so effective in reducing friction and wear at solid interfaces. To this extent, the application of tools like ab initio molecular dynamics based on first-principle density functional theory is severely hindered by the size of the systems of interests and the need to simulate their dynamics over relatively long times. To enable tribological simulations with quantum accuracy for a first time, we develop a workflow for smart configuration sampling in active learning, to obtain machine learning interatomic potentials which are shown to be sufficiently robust and accurate also in the characteristic harsh conditions generated by high loads and shear rates. Focusing on glycerol rich lubricants, we apply this active learning strategy to generate a neural network potential to simulate the formation and behavior of nanometer thick molecular tribofilms. The simulations reveal the superior accuracy of the machine learning approach with respect to classical molecular dynamics with reactive force fields, and pave the way for more promising in depth exploration of novel carbon-based lubricants.

Transition Metal (Cu, Pd, and Ag)-Modified Nb2S2C Monolayer for Highly Efficient Catechol Sensing: A First-Principles Investigation.

Motivated by recent advancements and the escalating application of two-dimensional (2D) gas or molecule sensors, this study explores the potential of the 2D Nb2S2C monolayer for detecting biomolecule catechol (Cc), whose excess concentration is highly dangerous to living beings. We use first-principles density functional theory (DFT) calculations to assess the Cc sensing performance of pure and transition metal (TM = Cu, Pd, Ag)-modified Nb2S2C monolayers. The Nb2S2C monolayer belonging to the new class of synthesized 2D materials, TM carbo-chalcogenides (TMCC), combines distinctive properties from both TM dichalcogenides and TM carbides and exhibits physisorption (-0.66 eV) toward the Cc molecule. Notably, the surface modifications with these TMs significantly enhanced the adsorption energy of Cc. The chemisorption of the Cc molecule on the Pd to Cu-modified monolayer is demonstrated with adsorption energies ranging from -1.09 to -1.3 eV and is due to the robust charge transfer and orbital interactions between the valence orbitals of TMs and Cc. In addition, the modification of the surface by TM leads to an increased work function sensitivity toward the Cc molecule. The study establishes the thermal stability at 300 K and dynamic stability of TM-Nb2S2C through ab initio molecular dynamics (AIMD) simulations and Phonon calculations, respectively. The theoretical estimation of achievable recovery time at 400 and 450 K for Pd and Ag and at 500 K for the Cu-modified Nb2S2C monolayer, respectively, confirms the potential practical application of the sensor for Cc detection. These compelling characteristics position the Nb2S2C monolayer as a promising nanomaterial for detecting Cc molecules in the environment.

Understanding the phase stability in a multi-principal-component AlCuFeMn alloy

Method(s) that can reliably predict phase evolution across thermodynamic parameter space, especially in complex systems, are of critical significance in academia as well as in the manufacturing industry. In the present work, the phase stability in an equimolar AlCuFeMn multi-principal-component alloy (MPCA) was predicted using complementary first-principles density functional theory calculations and ab initio molecular dynamics (AIMD) simulations. The temperature evolution of completely disordered, partially ordered, and completely ordered phases was examined based on the Gibbs free energy. Configurational, electronic, vibrational, and lattice mismatch entropies were considered to compute the Gibbs free energy of the competing phases. Additionally, elemental segregation was studied using AIMD. The predicted results at 300 K align well with room-temperature experimental observations using x-ray diffraction and scanning and transmission electron microscopy on a sample prepared using commercially available pure elements. The adopted method could help in predicting plausible phases in other MPCA systems with complex phase stability.

Density functional theory of the effect of different directional strains on the physical properties of coal

The effects of different directional strains on the physical properties of coal were studied using the first-principles density functional theory (DFT). The results show that the effect of strain on the physical properties of coal is mainly in the range of 0–8 % strain and greater than 8 % strain. When the strain is less than 8 %, in the elastic range, strain leads to an increase in the strain energy and stress of the coal, a decrease in deformation resistance, and better thermal stability. The bandgap of coal is 1.42 eV; the bandgap width decreases and the electrical conductivity increases with an increase in strain. Charge transfer in coal mainly occurs around O and N atoms due to their stronger electronegativity; strain has a great effect on the relative positions of the atoms. In this range, the effect of strain on the optical properties of coal is regular. With strain exceeding 8 %, the coal structure loses stability and is in the plastic range. This leads to significant changes in the mechanical properties, stability, electronic structure, and optical properties of coal with poor regularity. The results provide a theoretical basis for understanding the relationship between the molecular structure of coal and its macroscopic properties.

ANN and DFT investigation of 55-atom icosahedral Ag-Pt nanoalloys: Understanding structure, dynamics, and [formula omitted] activation

An artificial neural network (ANN)–based interatomic potential has been constructed to examine the structural properties of Ag55−nPtn nanoalloys, where n= 0–14. We conducted molecular dynamics simulations for global-optimizations of these nanoalloys using ANN-based interatomic potential. The relative stability of the Ag-Pt nanoalloys has been studied using stability indicators such as cohesive energy, excess energy and interaction energy. Additionally, we analyse the adsorption of O2 and CO molecules on Ag55−nPtn nanoalloys using the first-principles density functional theory based (DFT) method. The presence of Pt doping has been found to increase the adsorption strength of O2 and CO on the Ag55−nPtn nanoalloys compared to the pure Ag55 nanocluster. Our investigation suggests that the presence of Pt atoms in the core of the nanoalloy has a relatively minor effect on the adsorption of O2 and CO in comparison to Pt atoms present on the surface. The adsorption of O2 and CO on Ag41Pt14 nanoalloy, in which one of the Pt atoms is present at the surface of the nanoalloy, shows strongest adsorption among all the compositions of Ag55−nPtn nanoalloys.

Nonvolatile ferroelectric control of both magnetic anisotropy and half-metallicity in multiferroic heterostructures GdI2/Al2Te3

Nonvolatile all-electric spin manipulation is optimal for low-power and compact spintronic devices. Herein, using first-principles density functional theory, we propose a bilayer van der Waals (vdW) multiferroic heterostructure (HS) GdI2/Al2Te3 constructed of ferromagnetic electride GdI2 and ferroelectric (FE) semiconductor Al2Te3 to possess robust magnetoelectric coupling near room temperature. By reversing the electrical polarization states in Al2Te3, the magnetoelectric coupling not only allows the reversible switch of GdI2 from semiconductor to half-metal but also promotes the reversible transition of magnetocrystalline anisotropy from in-plane to out-of-plane. More importantly, the high Curie temperature (TC) of GdI2 and the unspoiled semiconducting nature of Al2Te3 in the HS predict the practical feasibility of this spin manipulation. Additionally, GdI2 exhibits substantial valley polarization when its magnetization direction changes to out-of-plane. These findings pave the way for achieving robust and efficient spin manipulation through all-electric control and also provide implications for multiferroic memory devices with highly efficient data reading and writing based on the HS.

Controlling structural, electronic and optical properties of cubic FASnI3 perovskites using biaxial strains in the presence of spin orbit coupling: A DFT analysis

There is a significant research focus on the utilization of organic-inorganic hybrid perovskite materials in the field of photovoltaics. The remarkable electronic and optical characteristics of organic-inorganic hybrid perovskites are prevalent in solar applications. In this study, the first-principles density functional theory (DFT) was used to investigate how strains affect the structural, electronic, and optical properties of the formamidinium tin tri-iodide (hereafter FASnI3) perovskite structure. The band structure analysis revealed that FASnI3 possesses semiconductor properties. A direct bandgap of 0.96 eV was found at the R-point for unstrained planar FASnI3 structure. The bandgap was reduced when compressive strains were applied. In contrast, the bandgap attained a higher value due to the increased tensile strains. Moreover, the optical properties, such as absorption coefficient, dielectric function and electron loss function, showed that FASnI3 structures have good photo-absorption ability. The dielectric constant exhibited a redshift in its peaks as the compressive strains were increased. However, the dielectric peaks exhibited a blueshift when subjected to the tensile strains. Additionally, for a deeper understanding of the band structure, the effect of spin-orbit coupling (SOC) was considered. The band gap of the FASnI3 perovskite structure was 0.75 eV when the SOC effect was considered. The strain is a crucial factor to consider for optimizing the performance of FASnI3 perovskite structure for their applications in optoelectronic devices.

Enhanced CO2 photoreduction to CH4 via *COOH and *CHO intermediates stabilization by synergistic effect of implanted P and S vacancy in thin-film SnS2

Reduction of CO2 to value-added hydrocarbons through artificial photosynthesis is one of the way to address the energy crisis and climate change issues. It is known that lowering the activation energy of CO2 molecules on the photocatalyst surface and key intermediates is crucial in photocatalytic CO2 reduction. Herein, we present phosphorus-implanted 20-nm SnS2 continuous thin film with sulfur vacancies (i.e., SV-SnS2:P where P substitutes on S sites). The fabrication process involves thermal evaporation, post-sulfurization, and ion implantation. Our gas-phase photocatalytic experiments show an enhanced and selective CO2 photoreduction to CH4 with a yield of 0.13 µmol cm−2 and selectivity of 92 % under solar-light irradiation for 4 h over an optimal ∼4.5 % P and ∼16 % SV. Experimental observations, conducted through X-ray absorption near edge, in situ near ambient pressure X-ray photoelectron, and in situ Fourier transform infrared spectroscopies, along with first-principle density functional theory calculations. Results reveal that P dopant is significantly affected by nearby SV via local charge density transfer from P to the nearest Sn and next-nearest S neighbor atoms, consequently, leads to the stabilization of *COOH and *CHO intermediates, where asterisks stand for P as the active site. Our results demonstrate how active site modulation, without using precious co-catalysts, plays a crucial role in intermediate stabilization in a wireless photocatalysis process.

Biotemplated Fe/La-co-doped TiO2 for photocatalytic depth treatment of compressed leachate from refuse transfer station.

Compressed leachate is a contaminated liquid containing various organic and inorganic pollutants produced in municipal refuse transfer stations, which pollute soil and groundwater, posing serious risks to the environment and human health. The Environmental Technology Co., Ltd. (Shenzhen, Guangdong Province, South China) treated compressed leachate obtained from a refuse transfer station. The chemical oxygen demand (COD) (641.2mg/L) of treated compressed leachate did not meet the wastewater quality standards in China for discharge into municipal sewers (COD ≤ 500mg/L) and the company's design discharge requirements (COD ≤ 400mg/L). Therefore, their further in-depth treatment is necessary. To this end, waste tobacco leaves were used as the biotemplate herein, and Fe/La-co-doped TiO2 (xFe,yLa)-TTiO2(g) was synthesized using a solvothermal-assisted biotemplating method. The photocatalytic depth treatment of compressed leachate was performed under simulated solar light using the prepared catalysts. After (3Fe,3La)-TTiO2(g) treatment, the COD of the leachate decreased from 641.2 to 280.1mg/L, and the COD removal rate was 1.2, 1.1, and 1.6 times higher than that of pure Fe-doped, La-doped and non-biological template TiO2, respectively. Characterization confirmed that the biological template endowed the catalyst with a unique morphology and high specific surface area. Its rich activity sites are conducive to enhancing the adsorption capacity of pollutants and providing an ideal place for photocatalytic reactions. Co-doping with iron and lanthanum ions altered the band structure of TiO2 and promoted the interconversion of Fe3+/Fe2+ and La3+/La2+ during photocatalysis. First-principles density functional theory simulations demonstrated that co-doping Fe and La in TiO2 created impurity levels that facilitated the transfer of photogenerated electrons. This study provides a new purification pathway for the depth treatment of compressed leachate.

Constant potential energetics of metallic and semiconducting electrodes: A benchmark study on 2D materials.

Grand-canonical (GC) constant-potential methods within an implicit solvent environment provide a general approach to compute the potential-dependent energetics at electrified solid-liquid interfaces with first-principles density-functional theory. Here, we use a mindfully chosen set of 27 isostructural 2D metal halides MX2 to analyze the variation of this energetics when the electronic structure changes from metallic to semiconducting and insulating state. Apart from expectable changes due to the opening up of the electronic bandgap, the calculations also show an increasing sensitivity to the numerical Brillouin zone integration and electronic smearing, which imposes computational burdens in practice. We rationalize these findings within the picture of the total interfacial capacitance arising from a series connection of the electrochemical double-layer capacitance and the so-called quantum capacitance resulting from the filling of electronic states inside the electrode. For metals, the electrochemical double-layer capacitance dominates at all potentials, and the entire potential drop takes place in the electrolyte. For semiconductors, the potential drop occurs instead fully or partially inside the electrode at potentials within or just outside the bandgap. For 2D semiconductors, the increased sensitivity to numerical parameters then results from the concomitantly increased contribution of the quantum capacitance that is harder to converge. Fortunately, this understanding motivates a simple extension of the CHE + DL approximation for metals, which provides the approximate GC energetics of 2D semiconductors using only quantities that can be obtained from computationally undemanding calculations at the point of zero charge and a generic double-layer capacitance.

Universal Machine Learning Kohn–Sham Hamiltonian for Materials

Abstract While density functional theory (DFT) serves as a prevalent computational approach in electronic structure calculations, its computational demands and scalability limitations persist. Recently, leveraging neural networks to parameterize the Kohn–Sham DFT Hamiltonian has emerged as a promising avenue for accelerating electronic structure computations. Despite advancements, challenges such as the necessity for computing extensive DFT training data to explore each new system and the complexity of establishing accurate machine learning models for multi-elemental materials still exist. Addressing these hurdles, this study introduces a universal electronic Hamiltonian model trained on Hamiltonian matrices obtained from first-principles DFT calculations of nearly all crystal structures on the Materials Project. We demonstrate its generality in predicting electronic structures across the whole periodic table, including complex multi-elemental systems, solid-state electrolytes, Moiré twisted bilayer heterostructure, and metal-organic frameworks. Moreover, we utilize the universal model to conduct high-throughput calculations of electronic structures for crystals in GNoME datasets, identifying 3940 crystals with direct band gaps and 5109 crystals with flat bands. By offering a reliable efficient framework for computing electronic properties, this universal Hamiltonian model lays the groundwork for advancements in diverse fields, such as easily providing a huge data set of electronic structures and also making the materials design across the whole periodic table possible.

Theoretical study on the structure, spectroscopic, and current–voltage behavior of 11-Cis and Trans retinal isomers in rhodopsin

In this study, the electronic transport properties of 11-Cis and Trans retinal, components of rhodopsin, were investigated as optical molecular switches using the nonequilibrium Green’s function (NEGF) formalism combined with first-principles density functional theory (DFT). These isomers, which can be reversibly converted into each other, were examined in detail. The structural and spectroscopic properties, including infrared (IR), Raman, nuclear magnetic resonance (NMR), and ultraviolet (UV) spectra, were analyzed using the hybrid B3LYP/6–311 + + G** level of theory. Complete vibrational assignments were performed for both forms utilizing the scaled quantum mechanical force field (SQMFF) methodology. To evaluate the conductivity of these molecules, we utilized current–voltage (I-V) characteristics, transmission spectra, molecular projected self-consistent Hamiltonian (MPSH), HOMO–LUMO gap, and second-order interaction energies (E2). The trendline extrapolation of the current–voltage plots confirmed our findings. We investigated the effect of different electrodes (Ag, Au, Pt) and various connection sites (hollow, top, bridge) on conductivity. The Ag electrode with the hollow site exhibited the highest efficiency. Our results indicate that the Cis form has higher conductivity than the Trans form.

Regioselective On-Surface Synthesis of [3]Triangulene Graphene Nanoribbons.

The integration of low-energy states into bottom-up engineered graphene nanoribbons (GNRs) is a robust strategy for realizing materials with tailored electronic band structure for nanoelectronics. Low-energy zero-modes (ZMs) can be introduced into nanographenes (NGs) by creating an imbalance between the two sublattices of graphene. This phenomenon is exemplified by the family of [n]triangulenes (n ∈ ). Here, we demonstrate the synthesis of [3]triangulene-GNRs, a regioregular one-dimensional (1D) chain of [3]triangulenes linked by five-membered rings. Hybridization between ZMs on adjacent [3]triangulenes leads to the emergence of a narrow band gap, Eg,exp ∼ 0.7 eV, and topological end states that are experimentally verified using scanning tunneling spectroscopy. Tight-binding and first-principles density functional theory calculations within the local density approximation corroborate our experimental observations. Our synthetic design takes advantage of a selective on-surface head-to-tail coupling of monomer building blocks enabling the regioselective synthesis of [3]triangulene-GNRs. Detailed ab initio theory provides insights into the mechanism of on-surface radical polymerization, revealing the pivotal role of Au-C bond formation/breakage in driving selectivity.

Electromechanical strain response of phosphorene nanotubes

Nanomaterials that undergo structural or other property changes upon application of external stimuli are called stimuli responsive materials and are particularly suited for drug delivery, biosensing or artificial muscle applications. Two-dimensional (2D) black phosphorus is an ideal material for such applications due to its remarkable electromechanical response. Given that one-dimensional (1D) black phosphorus nanotubes (PNTs) are calculated to be energetically stable, it is possible that they can undergo similar electromechanical responses to their 2D counterparts, allowing their potential application as nanochannel devices for drug delivery. Using first-principles density functional theory, we investigated the electromechanical response of different-sized PNTs upon charge injection. Upon hole injection, the diameter of the PNTs expands up to a maximum of 30.2% for a (0,15) PNT that is 0.24 nm in diameter. The PNTs become highly p-doped as the valence band maximum crosses the Fermi level and undergoes switching from a direct to indirect band gap. The mechanism behind the electromechanical response was determined through analysis of the structural deformations, charge density distribution and Bader partial charges. It was shown that injection of charge alters the Young’s Modulus of the PNTs, as hole injection weakens the structural integrity of the nanotube, allowing a greater electromechanical response, with PNT-15 showing the largest decrease in the Young’s Modulus of 15.34%. These findings show that 1D PNTs are promising materials for the development of nanoelectromechanical actuators which could be used for drug delivery, energy harvesting or similar applications.