eV Barrier Research Articles

Copper diffusion hindrance in Ti-TM (TM = W, Ru) alloys: A first-principles insight

This study utilizes DFT calculations to assess the effectiveness of Ti-TM (TM = W, Ru) alloys in obstructing copper diffusion, a pivotal factor for semiconductor device reliability. The calculated diffusion barriers for Cu in TiRu and Ti4W12 alloys are found to be 0.48 eV and 0.34 eV, respectively, significantly surpassing the 0.25 eV barrier for Cu diffusion in Si. This comparative analysis highlights the enhanced diffusion resistance of these alloys, with TiRu displaying a barrier nearly twice that of Si. An in-depth examination of the electronic structure and microstructural attributes of the alloys indicates that atomic interactions at the Cu/Ti-TM interface play a crucial role in hindering Cu diffusion. The local density of states, charge density differences, and electron localization functions were scrutinized to clarify the nature of these interactions. The research uncovers that the combined action of Ru, W, Cu, and Ti atoms leads to a synergistic strengthening of the diffusion barrier, implying a robust interatomic repulsion that restricts Cu migration. The findings contribute to a deeper fundamental understanding of Cu diffusion mechanisms in Ti-TM alloys and offer a scientific basis for the judicious selection of materials for diffusion barrier layers. The study supports the further exploration and potential application of TiRu and Ti4W12 alloys in the semiconductor industry.

Selective direct deoxygenation of m-cresol on Heusler alloy catalysts via precise control of electronic structure: An integrated density function theory and microkinetic modeling study

Directional designing a catalyst with high direct deoxygenation selectivity of Phenols during hydrodeoxygenation (HDO), remains a formidable challenge in cost-effectively converting biomass to bio-fuel and chemicals. Herein, we evaluated for the first time the catalytic performance of Heusler alloy surfaces for HDO process of m-cresol at the atomic scale. The direct deoxygenation (DDO) route of m-cresol on the Co2FeGa (110) surface at 573.15 K exhibited relatively low kinetic (1.20 eV) and thermodynamic (−0.04 eV) barriers, leading to high selectivity (near 100 %) for toluene production. The degree of rate control (DRC) analysis revealed that direct dehydroxylation constituted the rate-limiting elementary reaction. Additionally, by tailoring the Ga and Ge ratio on the Co2FeGa1-xGex (110) surface, an almost linear relationship (R2 = 0.95) was discovered between activation energy of C-OH and the d-band center energy of the Fe element in the unit cell. Both the activation energy of C-OH and d-band center energy of the Fe decreased with increasing Ge/Ga substitution ratio. This research unveils for the first time the catalytic performance of Heusler alloy for the selective direct deoxygenation of m-cresol, but also suggest the possibility tuning d-band center of Heusler alloys to precisely tailor the selectivity of DDO during HDO process.

Electrochemical Reduction of N2 to Ammonia Promoted by Hydrated Cation Ions: Mechanistic Insights from a Combined Computational and Experimental Study.

Alkali ions, major components at the electrode-electrolyte interface, are crucial to modulating reaction activity and selectivity of catalyst materials. However, the underlying mechanism of how the alkali ions catalyze the N2 reduction reaction (NRR) into ammonia remains elusive, posing challenges for experimentalists to select appropriate electrolyte solutions. In this work, by employing a combined experimental and computational approach, we proposed four essential roles of cation ions at Fe electrodes for N2 fixation: (i) promoting NN bond cleavage; (ii) stabilizing NRR intermediates; (iii) suppressing the competing hydrogen evolution reaction (HER); and (iv) modulating the interfacial charge distribution at the electrode-electrolyte interface. For N2 adsorption on an Fe electrode with cation ions, our constrained ab initio molecular dynamic (c-AIMD) results demonstrate a barrierless process, while an extra 0.52 eV barrier requires to be overcome to adsorb N2 for the pure Fe-water interface. For the formation of *NNH species within the N2 reduction process, the calculated free energy barrier is 0.50 eV at the Li+-Fe-water interface. However, the calculated barrier reaches 0.81 eV in pure Fe-water interface. Furthermore, experiments demonstrate a high Faradaic efficiency for ammonia synthesis on a Li+-Fe-water interface, reaching 27.93% at a working potential of -0.3 V vs RHE and pH = 6.8. These results emphasize how alkali metal cations and local reaction environments on the electrode surface play crucial roles in influencing the kinetics of interfacial reactions.

Advancing CO2 hydrogenation to formic Acid: DFT insights into Frustrated Lewis Pair−Functionalized UiO−67 catalysts

In this study, we explore the potential of metal–organic frameworks (MOFs) as catalysts for converting CO2 into valuable chemicals. The focus is on integrating frustrated Lewis pairs (FLPs) within the UiO−67 framework. We investigated 12 distinct functionalized FLP moieties (X = −BF2, −BCl2, −BBr2, −BH2, −B(CH3)2, −B(CF3)2, −B(CN)2, −B(NO2)2, −B(OH)2, −B(NH2)2, −B(OCH3)2, and −B(N(CH3)2)2 to determine their ability to activate small molecules within heterogeneous catalysis using density functional theory (DFT). This study reveals two critical stages in the CO2 conversion process with H2 in UiO−67−X. First, the initial heterolytic cleavage of H2 at the FLP site, and second, the subsequent hydrogenation of CO2. The latter involves the addition of a hydride and a proton. Our findings demonstrate that these modifications facilitate efficient dissociation of H2 into Hδ− and Hδ+ with energy barriers ranging from 0.12 to 0.87 eV and CO2 hydrogenation barriers spanning from 0.61 to 1.90 eV. Notably, the −B(CH3)2 functional group exhibited superior effectiveness in CO2 hydrogenation to formic acid (HCOOH; FA). This enhanced activity correlates directly with FLP acidity and the Gibbs free energy changes in H2 dissociation reaction. It highlights the significant influence of FLP−assisted heterolytic dissociation of H2 in the CO2 conversion process. The results of this study do more than introduce metal-free heterogeneous FLPs within MOFs. They also establish a clear link between the functional group composition, FLP acidity, and catalytic efficiency. These insights offer a valuable theoretical foundation for the design of advanced UiO−67−X catalysts. They open up possibilities for transforming greenhouse gases into valuable chemical products, contributing to sustainable chemical synthesis.

Adsorption, dissociation, and diffusion of borazine on Pt(111)

Using first-principles calculations, we investigate the adsorption, dissociation, and diffusion of borazine, a common precursor for the growth of two-dimensional hexagonal boron nitride (h-BN), on a Pt(111) surface. Our calculations show that borazine adsorbs on Pt(111) both molecularly and dissociatively. The molecular borazine has a planar structure, whereas the dissociated borazine is either in a tilted or vertical configuration. The energy differences between the structures are only ∼0.1 eV although the dissociated ones are more stable, and the energy barriers for conversion between the structures are also of the order of 0.1 eV. For molecular adsorption, borazine migrates through direct (0.87 eV barrier) or rotational (0.67 eV barrier) mechanisms. In the dissociated state, with alternating parallel and perpendicular structures, the borazine radical can migrate via a “slinky” movement. This results in a much lower diffusion barrier of 0.2 eV. In the case of vertical diffusion, the radical migrates with an energy barrier of 0.29 eV. Our results are consistent with experimental observations of borazine dehydrogenation and may be helpful in understanding h-BN formation at room temperature. We also discuss the atomistic processes for h-BN formation at high growth temperatures.

Excited-state dynamics of deuterated indigo

Indigo, a rich blue dye, is an incredibly photostable molecule that has survived in ancient art for centuries. It is also unique in that it can undergo both an excited-state hydrogen and proton transfer on the picosecond timescale followed by a ground-state back transfer. Previously, we performed gas phase excited-state lifetime studies on indigo to study these processes in a solvent-free environment, combined with excited-state calculations. We found two decay pathways, a fast sub-nanosecond decay and a slow decay on the order of 10 ns. Calculations of the excited-state potential energy surface found that both hydrogen and proton transfer are nearly isoenergetic separated by a 0.1 eV barrier. To further elucidate these dynamics, we now report a study with deuterated indigo, using resonance-enhanced multi-photon ionization and pump-probe spectroscopy with mass spectrometric isotopomer selection. From new calculations of the excited-state potential energy surface, we find sequential double-proton or hydrogen transfer, whereby the trajectory to the second transfer passes a second barrier and then encounters a conical intersection that leads back to the ground state. We find that deuteration only increases the excited-state lifetimes of the fast decay channel, suggesting tunneling through the first barrier, while the slower channel is not affected and may involve a different intermediate state.Graphical abstract

First-principles study of Li adsorption and diffusion in naphyne

The Li adsorption and diffusion properties in naphyne are explored by first-principles calculations. The porous structure of naphyne facilitates the adsorption of Li atoms, and the adsorption performance of large pores is better than that of small pores. The average open circuit potential is 0.78 V and the maximum Li storage capacity of bulk naphyne is up to 620 mAh/g, much larger than the up limit of the popular graphite. Upon Li intercalation, the interlayer spacing dilatation of bulk naphyne is only 1.78 %, implying that naphyne would not undergo significant structural degradation during cycling. The average adsorption energy between Li and naphyne in LiC3.6 is −2.38 eV/Li, which is feasible to realize their free migration. The porous structure enables Li atoms to diffuse either parallel or perpendicular to the naphyne plane. About 0.41–0.70 eV barriers are needed to overcome for the three-dimensional Li diffusion. Compared to commercial graphite, the higher Li capacity, the smaller structural distortion, and the unique three-dimensional diffusion performance of Li atoms make naphyne a promising candidate as the anode material of LIB.

La/Ge stacked nanosheets designed as optical resonators, microwave oscillators and 5 G/6 G gigahertz receivers

Glass/Ge and La/Ge stacked layers, 100 nm thick, were prepared via thermal evaporation under a vacuum pressure of 10−5 mbar. Structural analysis confirmed amorphous growth of Ge nanosheets. Optically coating Ge onto La improved light absorption, energy band gap, and dielectric responses. In addition, dielectric spectra fitting using Lorentz approach showed increased free electron density, plasmon frequency, and drift mobility (up to 1153 cm2/Vs) in Ge due to lanthanum presence. Moreover, LGA Schottky barrier devices (La/Ge/Au) exhibited tunneling-type current conduction with 0.815 eV barrier height and 40 nm width. Resistance spectra of these Schottky barriers displayed negative resistance near 0.40 GHz, while capacitance spectra showed resonance-antiresonance behavior. La/Ge and LGA interface can be utilized for optical receivers and microwave resonators in 5 G/6 G technologies.

Adaptable platform for trapped cold electrons, hydrogen and lithium anions and cations

Cold cations, electrons and anions are ubiquitous in space, participate in star formation chemistry and are relevant to studies on the origin of molecular biology homochirality. We report on a system to generate and trap these species in the laboratory. Laser ablation of a solid target (LiH) facing a sublimating Ne matrix generates cold electrons, anions, and cations. Axial energy distributions (of {{{{{{rm{e}}}}}}}^{-}, {{{{{{rm{H}}}}}}}^{pm } and {{{{{{rm{Li}}}}}}}^{pm }) peaked at 0–25 meV are obtained in a Penning trap at 90 mT and 0.5 eV barrier. Anions can be guided and neutralized with low recoil energy by near–threshold photodetachment. An immediate prospect for this {{{{{{rm{H}}}}}}}^{-} source is to load hydrogen atoms into the ALPHA antihydrogen trap at CERN toward direct spectroscopic comparison of both conjugated species beyond 13 significant figures. The production is potentially scalable and adaptable to different species including deuterium and tritium, relevant for neutrino mass and fusion research.

Computational Screening of La2NiO4+δ Cathodes with Ni Site Doping for Solid Oxide Fuel Cells.

Doping on the crystal structure is a common strategy to modify electronic conductivity, ion conductivity, and thermal stability. In this work, a series of transition metal elements (Fe, Co, Cu, Ru, Rh, Pd, Os, Ir, and Pt) doped at the Ni site of La2NiO4+δ compounds as cathode materials of solid oxide fuel cells (SOFCs) are explored based on first-principles calculations, through which the determinant factors for interstitial oxygen formations and migrations are discussed at an atomistic level. The interstitial oxygen formation and migration energies for doped La2NiO4 are largely reduced in contrast to the pristine La2NiO4+δ, which is explained by charge density distributions, charge density gradients, and Bader charge differences. In addition, based on a negative correlation between formation energy and migration barrier, the promising cathode materials for SOFCs were screened out between the doped systems. The Fe-doped structures of x = 0.25, Ru-doped structures of x = 0.25 and x = 0.375, Rh-doped structures of x = 0.50, and Pd-doped structures of x = 0.375 and x = 0.50 are screened out with interstitial oxygen formation energy less than -3 eV and migration barrier less than 1.1 eV. In addition, DOS analysis indicates that doping to La2NiO4+δ also facilitates the electron conductions. Our work provides a theoretical guideline for the optimization and design of La2NiO4+δ-based cathode materials by doping.

Atomic Scaled Depth Correlation to the Oxygen Reduction Reaction Performance of Single Atom Ni Alloy to the NiO2 Supported Pd Nanocrystal.

This study demonstrates the intercalation of single-atom Ni (NiSA ) substantially reduces the reaction activity of Ni oxide supported Pd nanoparticle (NiO2 /Pd) in the oxygen reduction reaction (ORR). The results indicate the transition states kinetically consolidate the adsorption energy for the chemisorbed O and OH species on the ORR activity. Notably, the NiO2 /Ni1 /Pd performs the optimum ORR behavior with the lowest barrier of 0.49eV and moderate second-step barrier of 0.30eV consequently confirming its utmost ORR performance. Through the stepwise cross-level demonstrations, a structure-Eads -ΔE correspondence for the proposed NiO2 /Nin /Pd systems is established. Most importantly, such a correspondence reveals that the electronic structure of heterogeneous catalysts can be significantly differed by the segregation of atomic clusters in different dimensions and locations. Besides, the doping-depth effect exploration of the NiSA in the NiO2 /Pd structure intrinsically elucidates that the Ni atom doping in the subsurface induces the most fruitful NiSA /PdML synergy combining the electronic and strain effects to optimize the ORR, whereas this desired synergy diminishes at high Pd coverages. Overall, the results not only rationalize the variation in the redox properties but most importantly provides a precision evaluation of the process window for optimizing the configuration and composition of bimetallic catalysts in practical experiments.

Photocatalytic property of two dimensional heterostructure MoS2/WS2 for hydrogen evolution via water splitting; a first principles calculation

We investigated photocatalytic property of two dimensional heterostructure MoS2/WS2 by a first principles calculation. Firstly, we evaluated the energetic stability of different heterostructures by comparing combination energies of heterojunctions with those between adjacent layers in multilayer MoS2 or WS2 system after constructing nine heterostructures (MoS2)n/(WS2)m (n, m = 1, 2, 3). The subscripts n and m are the numbers of MoS2 or WS2 layers that are contained in the above heterostructures, respectively. The investigated heterostructures have all stable binding energy of about 0.2 eV. Secondly, we calculated band gap of every heterostructure in order to compare it with the oxidation/reduction level for water splitting. Among the considered nine structures, the heterostructure (MoS2)1/(WS2)1 is suitable for overall water splitting because it has a band gap of 1.70 eV and energy barrier of 0.21 eV for preventing recombination of electrons and holes generated by light irradiation. In addition, the heterostructure is also favorable to the evolution of hydrogen, as it has a low hydrogen desorption energy of 0.035 eV.

The rare earth doped Mg2Ni (0 1 0) surface enhances hydrogen storage

Rare earth doping has been proved to be an effective method to improve hydrogen storage properties of Mg-based alloys. In this work, the effect of rare earth (Y, Ce, La, Sc) doping on the thermal stability, electronic property and hydrogen adsorption/desorption behavior of Mg2Ni (010) surface are systematically investigated by first principles calculation. The results show that rare earth doping in Mg2Ni (010) surface are thermodynamic feasible. The calculated electronic structures shown that rare earth atoms weaken the binding strength between H and Mg2Ni (010) substrate, thus reduce the hydrogen diffusion and desorption energies barriers, and improve the hydrogen storage properties of Mg2Ni. Among the four rare earth elements, Ce shows the best potential. Notably, the substitution doping of Ce to Mg atom significantly reduces the H diffusion barrier by 0.32 eV and H2 desorption barrier by 1.0 eV. This discovery provides a direction for the preparation of rare earth doped Mg2Ni hydrogen storage materials.

Polarization modulation of 2DEG toward plasma-damage-free GaN HEMT isolation

GaN electronics have hinged on invasive isolation such as mesa etching and ion implantation to define device geometry, which, however, suffer from damages, hence potential leakage paths. In this study, we propose a new paradigm of polarization isolation utilizing intrinsic electronic properties, realizing in situ isolation during device epitaxy without the need of post-growth processing. Specifically, adjacent III- and N-polar AlGaN/GaN heterojunctions were grown simultaneously on the patterned AlN nucleation layer on c-plane sapphire substrates. The two-dimensional electron gas (2DEG) was formed at III-polar regions but completely depleted in N-polar regions, thereby isolating the 2DEG channels with a large 3.5 eV barrier. Structures of polarization-isolated high electron mobility transistors (PI-HEMTs) exhibit significantly reduced isolation leakage currents by up to nearly two orders of magnitude at 50 V voltage bias compared to the state-of-the-art results. Aside from that, a high isolation breakdown voltage of 2628 V is demonstrated for the PI-HEMT structure with 3 μm isolation spacing, which is two-times higher than a conventional mesa-isolation HEMT. Moreover, the PI-HEMT device shows a low off-state leakage current of 2 × 10−8 mA/mm with a high Ion/Ioff ratio of 109 and a nearly ideal subthreshold slope of 61 mV/dec. This work demonstrates that polarization isolation is a promising alternative toward the plasma-damage-free isolation for GaN electronics.

Overcome energy loss of exciplex-sensitized fluorescence OLEDs with separating exciton generation and fluorescence emission zone

TADF-sensitizing-fluorescence (TSF) strategy suffered a disturbing energy loss causing by the T1 states of fluorescence dopant (FD) due to its low T1-state energy and forbidden of radiative transition. In this manuscript, we used TCTA/PO-T2T planar heterojunction (PHJ) interface as exciton generation zone and adjacent PO-T2T layer doped with rubrene as fluorescence emission zone, achieved the maximum EQE and CE of 8.3% and 26.1 cd A−1, respectively for rubrene-based device. Our experiments show the necessary PO-T2T thickness doped with rubrene is 15 nm and thicker doping layer over 15 nm would destroy device efficiency. It was further found that the exciplex exciton begin to decay within the time of 4 nm diffusion distance in PO-T2T layer and most of exciplex excitons were restrained in TCTA/PO-T2T heterojunction interface in PHJ device. The about 1.1 eV barrier for hole injection from TCTA to PO-T2T and bad hole-transporting capability of PO-T2T made exciple exciton only generate on this interface. Thus, even if the rubrene doped PO-T2T layer is right after the TCTA layer, FD in PO-T2T layer are well separated to the exciplex excitons in TCTA/PO-T2T interface, overcoming T1 energy loss caused by FD. Our approach provides a beneficial path towards overcome energy loss causing by the T1 states of FD in TSF-OLEDs based on exciplex as TADF sensitizer.

Methane conversion into C2 hydrocarbons promoted by N2 over MoP (001) surface: A DFT investigation

Herein, DFT calculations were employed to investigate direct CH4 catalytic conversion over MoP (001) surface. On the surface, CH4 decomposes completely with H2 formation, while C2 hydrocarbon formation is unlikely. Fortunately, N2 introduction would promote direct CH4 conversion into C2 hydrocarbons. N2* prefers to dissociate into two N* on the surface and complete CH4 decomposition is little influenced. While H2 formation is suppressed and a portion of H* adatoms are abstracted by N* resulting in NH3. Two C* intermediates from CH4 decomposition combine into C2* cluster with 1.35eV barrier. The two C of C2* capture H alternatively producing C2H4 and C2H6 finally. The rate-determining step with 1.78eV barrier happens in NH3 formation. Moreover, desorption of products is favorable, and separation of C2 hydrocarbons and NH3 is ease to achieve.

N2O decomposition on Ti3O6 deposited on anatase(1 0 1) from first-principles calculations: The role of oxygen vacancy†

Polarons induced by oxygen vacancy play a key role in many reactions on the reduced transition metal oxides. In this study, based on DFT + U calculations, we addressed the N2O decomposition on Ti3O6 cluster deposited on anatase(101). In the first half of the cycle, N2O adsorbed on the titanium atom of the cluster, resulting in the formation of N2 and O2 and oxygen vacancy. In the second one, another N2O interacted with the oxygen vacancy site to recreate the cluster, leaving an N2 molecule. The total dissociation energy of two subsequently adsorbed N2O molecules into 2 N2 and O2 is −0.15 eV. It is found that two polaron states appear in the presence of the oxygen vacancy. Based on the N2O adsorption energies, we discover that N2O decomposition take place in a geometry-dependent manner. In other words, among two different configurations proposed for N2O adsorption on Ti3O6@anatase(101) and Ti3O5@anatase(101) systems, only the decomposi- tion via the O-Ti pathway on Ti3O5@anatase(101) leads to the exothermic effect of −1.41 eV and energy barrier of 1.07 eV, which facilitates the decom- position of N2O on Ti3O5@anatase(101). Therefore, in order to obtain N2O dissociation on this cluster, the generation of the oxygen vacancy is crucial.

Topochemistry‐Driven Synthesis of Transition‐Metal Selenides with Weakened Van Der Waals Force to Enable 3D‐Printed Na‐Ion Hybrid Capacitors

AbstractHybrid capacitors exhibit promise to bridge the gap between rechargeable high‐energy density batteries and high‐power density supercapacitors. This separation is due to sluggish ion/electron diffusion and inferior structural stability of battery‐type materials. Here, a topochemistry‐driven method for constructing expanded 2D rhenium selenide intercalated by nitrogen‐doped carbon hybrid (E‐ReSe2@INC) with a strong‐coupled interface and weak van der Waals forces, is proposed. X‐ray absorption spectroscopy analysis dynamically tracks the transformation from ReO into ReC bonds. The bridging bonds act as electron transport channels to enable improved conductivity and accelerated reaction kinetics. The expanded interlayer‐spacing of ReSe2 layer by INC facilitates ion diffusion and ensures structural stability. As expected, the E‐ReSe2@INC achieves an improved rate capability (252.5 mAh g−1 at 20 A g−1) and long‐term cyclability (89.6% over 3500 cycles). Moreover, theoretical simulations reveal the favorable Na+ storage kinetics can be ascribed to its low bonding energy of −0.06 eV and diffusion barrier of 0.08 eV for sodium ions. Additionally, it is demonstrated that 3D printed sodium‐ion hybrid capacitors deliver high energies/power densities of 81.4 Wh kg−1/0.32 mWh cm−2 and 9992.1 W kg−1/38.76 mW cm−2, as well as applicability in a wide temperature range.

Stereodynamic Control of Collision-Induced Nonadiabatic Dynamics of NO (A2Σ+) with H2, N2, and CO: Intermolecular Interactions Drive Collision Outcomes.

Intermolecular interactions, stereodynamics, and coupled potential energy surfaces (PESs) all play a significant role in determining the outcomes of molecular collisions. A detailed knowledge of such processes is often essential for a proper interpretation of spectroscopic observations. For example, nitric oxide (NO), an important radical in combustion and atmospheric chemistry, is commonly quantified using laser-induced fluorescence on the A2Σ+ ← X2Π transition band. However, the electronic quenching of NO (A2Σ+) with other molecular species provides alternative nonradiative pathways that compete with fluorescence. While the cross sections and rate constants of NO (A2Σ+) electronic quenching have been experimentally measured for a number of important molecular collision partners, the underlying photochemical mechanisms responsible for the electronic quenching are not well understood. In this paper, we describe the development of high-quality PESs that provide new physical insights into the intermolecular interactions and conical intersections that facilitate the branching between the electronic quenching and scattering of NO (A2Σ+) with H2, N2, and CO. The PESs are calculated at the EOM-EA-CCSD/d-aug-cc-pVTZ//EOM-EA-CCSD/aug-cc-pVDZ level of theory, an approach that ensures a balanced treatment of the valence and Rydberg electronic states and an accurate description of the open-shell character of NO. Our PESs show that H2 is incapable of electronically quenching NO (A2Σ+) at low collision energies; instead, the two molecules will likely undergo scattering. The PESs of NO (A2Σ+) with N2 and CO are highly anisotropic and demonstrate evidence of electron transfer from NO (A2Σ+) into the lowest unoccupied molecular orbital of the collision partner, that is, the harpoon mechanism. In the case of ON + CO, the PES becomes strongly attractive at longer intermolecular distances and funnels population to a conical intersection between NO (A2Σ+) + CO and NO (X2Π) + CO. In contrast, for ON + N2, the conical intersection is preceded by an ∼0.40 eV barrier. Overall, our work shines new light into the impact of coupled PESs on the nonadiabatic dynamics of open-shell systems.

Multi-objective optimization of alkali/alkaline earth metals doped graphyne for ultrahigh-performance CO2 capture and separation over N2/CH4

Adsorbents with excellent CO2 capture and separation performances are critical in reducing the excessive CO2 concentration in the atmosphere. Herein, alkali/alkaline earth metals doped graphynes (AMn-GYs, AM = Li, Na, K, Mg and Ca; GY = graphyne; n = 0.5, 1, and 2) were evaluated by employing grand canonical Monte Carlo and density functional theory approaches. The results showed that AMs were strongly bonded on GY with binding energies of −0.09 to −2.52 eV and diffusion barriers of 5.20–16.32 eV. Electronic structure analyses proved that there was a strong covalent bond, large charge transfer, and distinct orbital overlap characters between the AMs and GY, thus constructing a stable and feasible gas adsorption environment. Among all structures, AM1-GYs with one AM doping in a GY unit cell displayed the best CO2 adsorption behavior. Thereafter, Li1/Na1/K1-GY with a pore size of 6.60 Å and Mg1/Ca1-GY with a pore size of 6.50 Å were screened as the potential adsorbents. In comparison, the best performing Ca1-GY had an ultra-high CO2 adsorption capacity of 9.01 mmol/g at 298 K and 1 bar, which was superior to most of the previously reported adsorbents. At 298 K and 1 bar, the CO2 selectivity over N2/CH4 for Ca1-GY reached 2246 and 5602, respectively. Interaction and gas distribution analysis confirmed that comparing to other AM1-GYs, Ca1-GY has a stronger affinity with CO2 and larger isosteric heat differences between CO2 and other gases, rendering Ca1-GY to possess excellent adsorption capacity and selectivity.