Potential Energy Profiles Research Articles

Excited state relaxation mechanisms of paracetamol and acetanilide.

The photochemical pathways of acetanilide and paracetamol were investigated using the XMS-CASPT2 quantum chemical method and the cc-pVDZ (correlation consistent polarized valence double- ) basis set. In both compounds, the bright state is the second excited state, designated as a La) state. Through a detailed exploration of the potential energy profile and the conical intersection structure between the La) and ground states, we gained a better understanding of how cleavage might occur in both molecules upon photoexcitation. Other potential relaxation mechanisms, including crossings with the dark and La) states, are also discussed in detail.

Synthesis of a highly programmable multistable Kresling origami-inspired unit cell

Multistable origami structures have been exploited for mechanical property tailoring, deployable robotic arms, wave propagation tuning and others, due to its ability to possess multiple stable states with distinct properties. Traditionally these structures are made by assembling bistable unit cells, which results in a significant increase in the size and weight of the system when larger number of stable states are required. Recently, researchers have uncovered a third stable state in the Kresling origami pattern. Although this is an advancement over the bistable unit cell, there is an unexplored opportunity for more systematically expanding the design space of Kresling unit cells to possess many more stable configurations (>>2) and enhance its programmable multistability. In this research, we seek to develop a methodology for the design of a Kresling origami-inspired unit cell that can be easily programmed to achieve up to 10 stable configurations, with the potential to achieve even more. We exploit the rich kinematics of the Kresling origami-inspired unit cell, that arise from its coupled translational and rotational deployment, and propose the strategic integration of tensile elements to realize multiple stable states. Analytically, we study the unstretched length values (defined to be the precise length between the string “slacked” and “tensioned” configurations) of the strings that yield the distinct number of stable states. We present the potential energy profiles with its corresponding force-displacement plots for the bistable, tristable, quadstable, pentastable and decastable unit cells. Moreover, we show that by simply adjusting the unstretched length of the strings we can program and tune the number of stable states of the unit cell. Tristable and pentastable unit cell prototypes are designed and experimentally tested to validate the proposed methodology. Lastly, a study is performed on the mechanical property tailoring capabilities of two unit cells assembled in series. The results show that the decastable unit cell assembly can achieve up to 55 discrete values of equivalent stiffness, while the bistable one can only achieve 3. For the bistable unit cell assembly to match this number, it will require 54 unit cells in series, which will significantly increase the size and weight of the structural system. These findings show that the modular structure will have more programmable capabilities, while maintaining its size and weight at a minimum, as the number of stable states per unit cell is increased.

Atmospheric Degradation Mechanism of Isoamyl Acetate Initiated by OH Radicals and Cl Atoms Revealed by Quantum Chemical Calculations and Kinetic Modeling.

Isoamyl acetate is one of the volatile organic compound class molecules relevant to agricultural and industrial applications. With the growing interest in isoamyl acetate applications in industry, the atmospheric fate of isoamyl acetate must be considered. Reaction mechanisms, potential energy profiles, and rate constants of isoamyl acetate reaction with atmospheric relevant oxidant OH radicals and Cl atoms have been obtained from the quantum chemical calculations and kinetic modeling. The geometry optimizations were conducted using M06-2X/6-311++G(3df,3pd) followed by single point-energy calculations at the DLPNO-CCSD(T) method with an extrapolated complete basis set. The rate constants were calculated by solving the master equation. A hydrogen-abstraction reaction dominates the first step of isoamyl acetate degradation, while the addition-substitution reaction plays a small role in the degradation products. The kinetic study was conducted to evaluate the rate constants within a temperature range of 200-400 K. The total rate constants for the isoamyl acetate degradation reactions initiated by the OH radical and Cl atom were determined to be 6.96 × 10-12 and 1.27 × 10-10 cm3 molecule-1 s-1, respectively, under standard temperature and pressure conditions. The product degradation mechanism, ozone formation potential, and atmospheric impacts were discussed.

Theoretical reaction kinetics predictions for acetone and ketene with NH2 radicals: Implications on acetone/ammonia kinetic modeling

The cross-reaction kinetics of acetone/ketene (CH3COCH3/CH2CO) + amino (NH2) radicals are first theoretically reported for a wide range of conditions (T = 300–2500 K and P = 0.1–100 atm) in this work. The high-level electronic structure method CCSD(T)/cc-pVnZ(n = T, Q)//B3LYP-D3BJ/6–311++G(d,p) is used to explore the potential energy profiles on which the temperature- and pressure-dependence kinetic behaviors of the title reactions are characterized using the Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) theory. Corrections of the one-dimensional hindered rotor approximation and asymmetric Eckart tunneling effect are also included in the rate constant calculations. Furthermore, this work delves into the competitive relationships among the H-abstraction, NH2 addition and addition-dissociation reaction pathways. For CH3COCH3 + NH2, the H-abstraction reaction of CH3COCH3 is highly favored over the addition-dissociation reaction and other isomerization channels. For CH2CO + NH2, the reaction channel of addition-dissociation to form CH2NH2 + CO under low temperature conditions is more advantageous, while the H-abstraction reaction plays a dominant role under combustion conditions (T ≥ 1000 K). To reveal the impact of the studied reaction kinetics on model predictions, the rate constants of dominant reaction channels calculated in this work are incorporated into a kinetic model for the auto-ignition, oxidation and pyrolysis of CH3COCH3/NH3 mixtures. The simulated results show that the effect of the updated rate constants on ignition delay time is mainly at low temperatures and the promotion effect of CH3COCH3 addition on the ignition of NH3 presents a nonlinear enhancement. The updated rate constants can also accelerate the consumption of CH3COCH3 and CH2CO formation, while also influence the concentration distributions of other significant species (e.g., NH3, CO). Therefore, the cross-reaction kinetics of CH3COCH3/CH2CO + NH2 are critical in controlling the fuel consumption, important intermediate formation and ignition delay time of CH3COCH3/NH3 mixtures.

A theoretical exploration of monomer activation mechanisms in bis-lithium N[sbnd]heterocyclic carbenes complexes for enhanced understanding of charge distribution in ring-opening polymerization of ε-caprolactone

A comprehensive examination was conducted on the ring-opening polymerization (ROP) mechanism of ε-caprolactone (ε-CL) employing bis-lithium N-heterocyclic carbene complexes (bisLiNHCs) in a theoretical framework. The modeled reactions were carried out utilizing density functional theory at B3LYP level. An activated-monomer mechanism was observed, characterized by occurrence of two distinct transition states. Initiating with activation of ε-CL via two lithium atoms from bisLiNHCs catalysts, the ensuing step involved nucleophilic addition of carbonyl group stemming from the lithium benzoxide (LiBnO) initiator. The ring opening ε-CL was accomplished via classical cleavage of acyl-oxygen bond. The determination of reaction barrier heights for ε-caprolactone with bisLiNHCs catalysts involved the examination of potential energy profiles. The computed energy profiles revealed exothermic characteristics for each ROP reaction, with the identification of a rate-determining step occurring at the second transition state, which entailed cleavage of acyl-oxygen bond from monomer. Furthermore, through comparisons catalytic capabilities of bisLiNHCs derivatives and energy barrier heights, it was observed that the length and flexibility of linker chain as well as steric effects from substituent groups, significantly influenced the geometric configuration. These specific variations induce alterations in both distance and angular orientation, which are pivotal aspects influencing the chelation dynamics between lithium and oxygen atoms.

On the link between the reaction force constant and conceptual DFT.

The reaction force constant ( ), introduced by Professor Alejandro Toro-Labbé, plays a pivotal role in characterizing the reaction pathway by assessing the curvature of the potential energy profile along the intrinsic reaction coordinate. This study establishes a novel link between and the reactivity descriptors of conceptual density functional theory (c-DFT). Specifically, we derive expressions that relate the reaction force constant to nuclear softness and variations in chemical potential. Our findings indicate that regions of the reaction pathway where is negative match with significant electronic structure rearrangements, while positive regions match mostly with geometric rearrangements. This correlation between and c-DFT reactivity descriptors enhances our understanding of the underlying forces driving chemical reactions and offers new perspectives for analyzing reaction mechanisms. The internal reaction path for the proton transfer in SNOH, chemical potential, and nuclear softness were computed using DFT with B3LYP exchange-correlation functional and 6-311++G(d,2p) basis set.

Atmospheric oxidation pathways of CF3CH2CFCl2 (HCFC-234fb) with OH-radicals and Cl-atoms: insights into the mechanism, thermodynamics, and kinetics.

The atmospheric oxidation of 1,1-dichloro-1,3,3,3-tetrafluoropropane, HCFC-234fb (DTP), leads to the formation of harmful radicals, contributing to stratospheric ozone depletion. Thus, a detailed study of the gas-phase oxidation of the first-generation chlorofluorocarbon alternative HCFC-234fb by a reaction with hydroxyl radicals and chlorine atoms is important to understand its harmful effects on the environment. In this work, we have performed quantum chemical calculations to investigate the thermodynamic and kinetic aspects of the titled reaction. The potential energy profile calculated at the CCSD(T)/aug-cc-pVTZ//MP2/cc-pVTZ level of theory shows that the major reaction pathway involves the abstraction of the H-atom from the central carbon atom, C2, giving rise to the product radical CF3C˙HCCl2F. The calculated rate-coefficients for the reaction with ˙OH and Cl-atoms are 3.89 × 10-15 and 2.54 × 10-17 cm3 molecule-1 s-1, respectively, at 298 K and are in accordance with the experimental rate coefficients. The results suggest that the rate-coefficient for the reaction of DTP with ˙OH is two orders of magnitude higher than that with Cl-atoms, indicating greater significance of the former reaction in the atmosphere. With the rate-coefficient values, the lifetime and the radiative efficiency were calculated to be 8.2 years and 0.246 W m-2 ppb-1, respectively. A 100-year global warming potential (GWP) of 712 was also estimated using the lifetime corrected radiative efficiency value.

Computational study on the Maillard reactions of glucose and galactose with lysine.

Milk has nutrient-rich but thermal sensitive matrix that undergoes varying degrees of Maillard reaction (MR) at heating conditions. The MR mainly occurs between lysine residues (Lys) and lactose composed of glucose (Glc) and galactose (Gal), which are abundantly sourced from dairy products. In the present study, the MRs of Glc and Gal with Lys at the initial and intermediate stages have been investigated theoretically using density functional theory (DFT) to simulate the gaseous and aqueous phases. Reaction mechanisms have been proposed, and relative energy changes of different steps were calculated according to the total mass balance. The calculations reveal that both Nα- and Nε-amine groups of Lys can react with the carbonyl functional group of Glc and Gal with the similar potential energy profiles, and Gal is more reactive than Glc. However, the barrier in Nε-channel is lower than in Nα-channel, indicating a faster reaction rate through the former channel compared with the latter. The 5-hydroxymethyl-2-furfural (HMF) and derivative are formed under 3-deoxysone route in the intermediate stage. The calculation results are helpful for proposing a reasonable MR mechanism and suggesting possible control methods of the MRs. In this study, different levels of DFT calculations have been conducted to investigate the mechanisms and favorability of generating MR products in Glc-Lys and Gal-Lys models at initial and intermediate stages in the gaseous and aqueous conditions. In order to elucidate the molecular models from the perspectives of chemistry and geometry, DFT calculations were performed by the mean of B3LYP functional at basis sets of 6-311 + + G (d, p) and 6-311 + + G (2df, 2p) with optional solvation settings. To examine the solvation effect, the study further constructed models with solvent H2O and calculated in wB97XD functional with 6-31 + G (d) basis set. All computations were carried out Gaussian 09 suite of quantum chemistry software.

Theoretical study on reaction kinetics of the absent HO2 concerted addition reaction on ester group of methyl esters: Case studies of methyl formate and methyl propanoate

In this work, a comprehensive study is performed to specify the contributions of H-abstraction, addition and addition-dissociation reactions of methyl esters + HO2, particularly to the low temperature oxidation. It is imperative to investigate these reactions in detail despite the generally higher bond strength of C=O compared to C=C. The two representative methyl esters, methyl formate (MF, HC(=O)OCH3) and methyl propanoate (MP, CH3CH2C(=O)OCH3), are chosen to theoretically explore the reaction kinetics of the C=O of ester group and HO2. The reaction pathways and potential energy profiles including H-abstraction, addition and addition-dissociation of MF+HO2 and MP+HO2 are investigated at the CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) and DLPNO-CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) level of theory, respectively. The rate constants of MF/MP + HO2 are determined by using the RRKM/master equation coupled with the 1-D hindered rotor approximation and Eckart tunneling correction. This work delves into the temperature and pressure-dependence of these reaction pathways, as well as the competition relationship among of them. The results indicate that for small ester (MF), the H-abstraction is more competitive across all reaction pathways, but under low temperature (≤ 700 K) and high pressure (≥ 10 atm) conditions, the collisional stabilization of peroxy-alcohol radicals (MF+HO2 = HO-ROO) becomes predominant. For larger ester (MP), this is not necessarily the case as such reactions are unimportant for combustion conditions (rates only appear at 400 K, 100 atm). Furthermore, to assess the impact of these reactions on kinetic modeling, the new rate constants of MF/MP + HO2 are incorporated into the kinetic models of MF and MP, respectively. The updated kinetic models reveal the significant role of H-abstraction reactions in ignition delay time and fuel consumption and the formation of peroxy-alcohol radicals is favorable for decomposition pathways, notably affecting fuel consumption at low temperatures. Consequently, this study highlights the important role of the HO2 addition to the C=O of ester group in the low temperature oxidation mechanism of methyl esters, which has been overlooked in previous studies.

A Competition among Three Ultrafast Photoinduced Events in Thiotropolone: Internal Conversion vs Intersystem Crossing vs ESIPT.

Gas phase excited-state quantum wavepacket dynamics simulations of the thiotropolone demonstrate the ultrafast triplet formation upon photoexcitation to the dipole-allowed S2 state. The dominant relaxation pathway of the S2-T4 intersystem crossing, facilitated by the strong spin-orbit coupling and narrow energy gap, competes with the S2 to S1/S3 internal conversion. The wavepacket populated in T4 via the former pathway decays to lower triplet states. Computed potential energy profiles suggest proton transfer via S2, which might compete with internal conversion and intersystem crossing. The nonadiabatic population transfer from the S2 to S1/S3 states enables proton transfer via the latter states, resulting in multiple proton transfer pathways. Experimental investigations are necessary to shed light on the complex ultrafast photodynamics of thiotropolone.

Excited-State Intramolecular Proton Transfer toward Conical Intersections in Indigo, Epindolidione, and Indirubin.

Indigo exhibits a high degree of photostability, experimentally supported by observations such as quenching of fluorescence and an exceptionally short excited-state lifetime. Epindolidione, a structural isomer of indigo, is highly fluorescent in contrast to indigo, while indirubin, another structural isomer, exhibits weak fluorescence similar to that of indigo. To elucidate the origin of the difference in photophysical and photochemical behavior, potential energy profiles of the excited-state intramolecular proton transfer in indigo, epindolidione, and indirubin are computationally studied by quantum chemical calculations using the TDDFT and extended MS-CASPT2 (XMS-CASPT2) methods. As a result, it is found that indigo and indirubin exhibit little energy barrier for the single proton transfer (SPT) in the S1(ππ*) state from the diketo to keto-enol form and low energy of the S1/S0 conical intersection (CI) in the latter form with a planar molecular structure. Epindolidione, on the other hand, exhibits much higher barriers for SPT and access to CI. These results suggest that the excited-state SPT and subsequent nonradiative deactivation via CI are more likely to occur in indigo and indirubin than in epindolidione, which is consistent with the experimental observations described above. For indigo and epindolidione, the deactivation channels via the second SPT from the keto-enol to dienol form are also compared.

Ab initio MO study on direct production of H2O, N2O and CO3 from the respective CH2OO “Bee-sting-like” attack at H2, N2 and CO2

ContextWe have computationally elucidated the mechanism for formation of H2O, N2O and CO3 from the reactions of CH2OO with H2, N2 and CO2, respectively, by the direct attack of the terminal O atom of CH2OO. This unique mechanism, which is characteristically “bee-sting-like” in nature, was found to be closely parallel to their reactions with the O(1D) atom. Reactions with H2 and CO2 take place by side-on attack, while the N2 reaction occurs by end-on attack with predicted barriers, 19.4, 13.1 and 25.3 kcal.mol−1, respectively. The CO2 reaction with CH2OO was found to occur by producing the C2v CO3, O = C < (O)O, instead of its D3h conformer, essentially similar to the O(1D) + CO2 reaction. The rate constants for the three reactions have been computed by the transition state theory (TST) based on the predicted potential energy profiles. We have also utilized the isodesmic nature of the dative bond exchange in the N2 reaction, CH2O → O + N2 = CH2O + N2 → O, to estimate the heat of the formation of CH2OO. Based on the heat of reaction computed at the highest level of theory employed, we obtained ΔfHo0 (CH2OO) = 27.5 kcal.mol−1; the value agrees with the recent results within ± 1 kcal.mol−1.MethodsAll calculations were performed using Gaussian 16 software. Geometry, frequency, and IRC analysis calculations were conducted at the M06-2X/aug-cc-pVTZ level of theory. The heats of reaction have been evaluated at the highest level, CCSD(T)/CBS(T,Q,5)//M06-2x/aug-cc-pvTz.

Computational Studies of Nucleophilic Substitution at Nitrogen Center: Reactions of NH2Cl with HO-, CH3O- and C2H5O.

The atomic-level mechanisms of the nucleophilic substitution reactions at the nitrogen center (SN2@N) were investigated for the reactions of chloramine (NH2Cl) with the alkoxide ions (RO-, where R = H, CH3, and C2H5) using DFT and MP2 methods. The computed potential energy profiles for the SN2@N pathways involving the back-side attack of the nucleophiles show the typical double-well potential with submerged barriers similar to the SN2@N reactions at the carbon center (SN2@C). However, the pre-reaction and post-reaction complexes are, respectively, the N-H…O and N-H…Cl hydrogen-bonded intermediates, which are different from those generally seen in SN2@C reactions. The SN2@N pathways involving front-side attack of the nucleophiles have high-energy barriers. The potential energy surfaces (PESs) along the proton-transfer pathways were flat. In addition to the proton-transfer and SN2 pathways, we also observed a new path for the methoxide and ethoxide nucleophiles where a hydride transfer from the nucleophile to chloramine resulted in the products Cl- + R'CHO + NH3, (R' = H, CH3), and was the most exoergic. A comparison of the energetics obtained used different DFT and MP2 methods with that of the benchmark coupled-cluster methods reveals that CAM-B3LYP best describes the PESs.

Competing C and N as Reactive Centers for Microsolvated Ambident Nucleophiles CN-(H2O)n=0-3: A Theoretical Study of E2/SN2 Reactions with CH3CH2X (X = Cl, Br, I).

As an ambident nucleophile, CN- has both C and N atoms that can act as the reactive center to facilitate substitution reactions. We investigate in detail the potential energy profiles of CN-(H2O)0-3 with CH3CH2X (X = Cl, Br, I) to explore the influence of solvent molecules on competition between the different nucleophilic atoms C and N involving the SN2 and E2 pathways. The energy barrier sequence for the transition states follows C@inv-SN2 < N@inv-SN2 < C@anti-E2 < N@anti-E2. When two different atoms act as nucleophilic atoms, the SN2 reaction is always preferred over the E2 reaction, and this preference increases with microsolvation. For the ambident nucleophiles CN-(H2O)0-3, C as the reactive center always has stronger nucleophilicity and basicity than N acting as the reactive center. Regarding the leaving group, the height of the energy barrier is positively correlated with the acidity of the CH3CH2X substrate for the E2 pathway and with X-heterolysis for the SN2 pathway. Furthermore, we found that in the gas phase, the energy barrier for different leaving group systems decreases gradually in the order Cl > Br > I, while in the SMD solution, the energy barrier and product energy increase slightly in the system from X = Cl to Br; this change may be due to the significantly weakened transition-state interaction for the X = Br system. Our activation strain, quantitative molecular orbital, and charge analyses reveal the physical mechanisms underlying the various computed trends. In addition, we also demonstrate the two points recently proposed by Vermeeren, P. . Chem. Eur. J. 2020, 26, 15538-15548.

Molecular Docking and Ligand-Binding Analysis of Amidine Derivatives TargetingPseudomonas aeruginosaandEscherichia coliBacterial Strains: AnIn SilicoApproach

Gram-negative bacteria represent a formidable challenge due to their exhibition of elevated resistance to various antibiotics. This study delves into the crisis posed by antimicrobial resistance (AMR), focusing on the alarming rise of bacteria (Gram-negative), such as Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), notorious for their severe infections. By examining the binding interaction with antibiotics (ampicillin, ciprofloxacin, trimethoprim, pentamidine, furamidine, and oligoamidine) and bacterial protein targets, the study utilized molecular docking and ligand-binding analysis. The result reveals different LibDock scores with the bacterial strain. Higher scores indicate stronger binding. Pentamidine exhibited the highest scores with all bacterial strains. CDOCKER energy due to interaction was computed to analyze the molecules binding with the bacteria, and pentamidine stood with higher CDOCKER value, indicating strong binding affinity. The work also assessed the antibiotics likeness using the rule of Lipinski’s five (RO5), and several antibiotics conform to the criteria. Molecular dynamics simulations were conducted to estimate compound stabilities, revealing stable conformations. The results revealed a stable potential energy (PE) profile for 5V7A Chain B. The RMSD profiles exhibited deviations within certain time intervals, indicating potential conformational changes in the antibiotics.

Enhancing Molecular Energy Predictions with Physically Constrained Modifications to the Neural Network Potential.

Exclusively prioritizing the precision of energy prediction frequently proves inadequate in satisfying multifaceted requirements. A heightened focus is warranted on assessing the rationality of potential energy curves predicted by machine learning-based force fields (MLFFs), alongside evaluating the pragmatic utility of these MLFFs. This study introduces SWANI, an optimized neural network potential stemming from the ANI framework. Through the incorporation of supplementary physical constraints, SWANI aligns more cohesively with chemical expectations, yielding rational potential energy profiles. It also exhibits superior predictive precision compared with that of the ANI model. Additionally, a comprehensive comparison is conducted between SWANI and a prominent graph neural network-based model. The findings indicate that SWANI outperforms the latter, particularly for molecules exceeding the dimensions of the training set. This outcome underscores SWANI's exceptional capacity for generalization and its proficiency in handling larger molecular systems.

Mechanism of Peroxynitrite Interaction with Ferric M. tuberculosis Nitrobindin: A Computational Study.

Nitrobindins (Nbs) are all-β-barrel heme proteins present along the evolutionary ladder. They display a highly solvent-exposed ferric heme group with the iron atom being coordinated by the proximal His residue and a water molecule at the distal position. Ferric nitrobindins (Nb(III)) play a role in the conversion of toxic peroxynitrite (ONOO-) to harmless nitrate, with the value of the second-order rate constant being similar to those of most heme proteins. The value of the second-order rate constant of Nbs increases as the pH decreases; this suggests that Nb(III) preferentially reacts with peroxynitrous acid (ONOOH), although ONOO- is more nucleophilic. In this work, we shed light on the molecular basis of the ONOO- and ONOOH reactivity of ferric Mycobacterium tuberculosis Nb (Mt-Nb(III)) by dissecting the ligand migration toward the active site, the water molecule release, and the ligand binding process by computer simulations. Classical molecular dynamics simulations were performed by employing a steered molecular dynamics approach and the Jarzynski equality to obtain ligand migration free energy profiles for both ONOO- and ONOOH. Our results indicate that ONOO- and ONOOH migration is almost unhindered, consistent with the exposed metal center of Mt-Nb(III). To further analyze the ligand binding process, we computed potential energy profiles for the displacement of the Fe(III)-coordinated water molecule using a hybrid QM/MM scheme at the DFT level and a nudged elastic band approach. These results indicate that ONOO- exhibits a much larger barrier for ligand displacement than ONOOH, suggesting that water displacement is assisted by protonation of the leaving group by the incoming ONOOH.

Loose bonding induced ultralow lattice thermal conductivity of a metallic crystal KNaRb

In the domain of metallic systems, electronic thermal conductivity typically governs heat transfer, while lattice (phononic) thermal conductivity (LTC) remains non-negligible magnitude. This study introduces the exceptional metallic material, cubic half-Heusler-type KNaRb, via phonon Boltzmann transport equation (BTE) resolution and first-principles calculations. KNaRb exhibits an ultralow LTC of 0.114 W/mK at room temperature, comparable to the lowest reported for metallic materials, contributing merely 0.66 % to overall thermal transport. Analysis attributes KNaRb's low LTC to low group velocity and strong anharmonicity, originating from its loosely bonded electronic structure. Acoustic modes, primarily from Rb atoms, dominate thermal transport. Examination of mean square displacement and potential energy profiles reveals significant movement of loosely bonded Rb atoms within KNaRb, acting as intrinsic "rattlers," inducing pronounced phonon anharmonicity and ultrashort lifetimes. This study advances understanding of heat conduction in metals, offering insights into materials with extremely low lattice thermal conductivity for potential future applications.

Energy and dynamics analysis of a single plucking energy harvester for transient-motion-powered IoT applications

This study focuses on a piezo-magneto-elastic structure comprising an economical piezoelectric cantilever and a magnet pair. It is designed for efficient mechanical energy harvesting to power a battery-free motion-sensing IoT system through plucking motions. We conduct a thorough analysis and parametric study to elucidate the energy and dynamic intricacies during operation, specifically under a single plucking excitation. Beginning with a magnetic dipole–dipole model, we present a potential energy profile to intuitively elucidate and quantitatively assess the energy progression throughout a single plucking transient. By meticulously adjusting the setup parameters, the input potential energy can be precisely tuned, ensuring that the energy harvested from a single plucking motion meets the demand of each round of wireless communication. Diverging from previous power-centric investigations of plucking energy harvesters, in which continuous plucking motions are investigated, our approach provides a new perspective on the energy-centric design and transient dynamics of a single plucking motion. The importance of the energy-matching concept considering the subsequent energy-driven electronic modules is emphasized. This insight offers valuable design principles for the effective energy-centric co-design of cyber-electromechanically coupled self-powered IoT systems.

Unraveling the Interactions between Lithium and Twisted Graphene.

Graphene is undoubtedly the carbon allotrope that has attracted the attention of a myriad of researchers in the last decades more than any other. The interaction of external or intercalated Li and Li+ with graphene layers has been the subject of particular attention for its importance in the applications of graphene layers in Lithium Batteries (LiBs). It is well known that lithium atoms and Li+ can be found inside and/or outside the double layer of graphene, and the graphene layers are often twisted around its parallel plane to obtain twisted graphene with tuneable properties. Thus, in this research, the interactions between Li and Li+ with bilayer graphene and twisted bilayer graphene were investigated by a first-principles density functional theory method, considering the lithium atom and the cation at different symmetry positions and with two different adsorption configurations. Binding energies and equilibrium interlayer distances of filled graphene layers were obtained from the computed potential energy profiles. This work shows that the twisting can regulate the interaction of bilayer graphene with Li and Li+. The binding energies of Li+ systematically increase from bilayer graphene to twisted graphene regardless of twisted angles, while for lithium atoms, the binding energies decrease or remain substantially unchanged depending on the twist angles. This suggests a higher adsorption capacity of twisted graphene towards Li+, which is important for designing twisted graphene-based material for LiB anode coating. Furthermore, when the Li or Li+ is intercalated between two graphene layers, the equilibrium interlayer distances in the twisted layers increase compared to the unrotated bilayer, and the relaxation is more significant for Li+ with respect to Li. This suggests that the twisted graphene can better accommodate the cation in agreement with the above result. The outcomes of this research pave the way for the study of the selective properties of twisted graphene.