Formation Energy Research Articles

Evaluation of Active Oxygen Species Derived from Water Splitting for Electrocatalytic Organic Oxidation

Active oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high‐value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au‐based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d‐band center of Au‐based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

A Systematic Local View of the Long-Term Changes of the Atmospheric Energy Cycle

Abstract The global climatology and long-term changes of the atmospheric energy cycle in the boreal winter are analyzed using a local available potential energy framework using the fifth generation ECMWF reanalysis data during 1979 to 2021. In contrast to the classic Lorenz energy cycle, this local framework provides the local information of available potential energy (APE) and its interactions with kinetic energy (KE), allowing the systematic study of barotropic and baroclinic processes. A further systematic decomposition of the APE and KE reservoirs into high- and low-frequency components is conducted to investigate the source and sink terms that account for their spatial variations and long-term changes. The climatology of the local energetics budget terms shows that the interplay between low-frequency APE and KE is mostly over the tropical and polar regions associated with the thermally direct circulation there. Interactions involving high-frequency components are mainly located in the storm track regions. We show that under recent global warming, a prominent dipolar trend of changes is present over the Asian-Pacific region for all energy forms. The long-term changes in the energy budget reveal how high-frequency APE intensification is due to a stronger conversion from low-frequency APE upstream of the storm track, and that this intensification can be compensated by eddy advection away from the storm track, rather than conversion to kinetic energy in the proximity of the mean jet. This provides evidence that a warmer climate substantially affects the energy cycle and, thus, the atmospheric circulation.

CaLi2PN3 - A Quaternary Chain-Type Nitridophosphate by Medium-Pressure Synthesis.

Nitridophosphates are in the focus of current research interest due to their structural versatility and properties, such as ion conductivity, ultra-incompressibility and luminescent properties when doped with suitable activator ions. Multinary representatives often require thorough investigation due to the competition with the thermodynamically more stable binary and ternary compounds. Another point of concern is the synthetic control of structural details, which is usually limited by conventional bottom-up syntheses. In this study, we report on the synthesis and characterization of the quaternary nitridophosphate CaLi2PN3. Various synthesis protocols were used for the preparation of CaLi2PN3, including the novel nitridophosphate double salt approach. The crystal structure was solved and refined from single-crystal X-ray diffraction data and confirmed by Rietveld refinement, solid-state NMR spectroscopy, EDX measurements and low-cost crystallographic calculations. The experimental results were corroborated by DFT calculations, which revealed the electronic band structure. Formation energy calculations allowed conclusions to be drawn about the stability in comparison to the initial ternary nitridophosphates. The synthesis of CaLi2PN3 exemplifies the enormous potential of medium-pressure syntheses in the field of nitridophosphate research. Furthermore, the presented new synthesis route allows a certain degree of structural control, which is a promising addition to previous synthesis strategies in nitridophosphate chemistry.

Low-Defect-Density Monolayer MoS2 Wafer by Oxygen-Assisted Growth-Repair Strategy.

Atomic chalcogen vacancy is the most commonly observed defect category in two dimensional (2D) transition-metal dichalcogenides, which can be detrimental to the intrinsic properties and device performance. Here a low-defect density, high-uniform, wafer-scale single crystal epitaxial technology by in situ oxygen-incorporated "growth-repair" strategy is reported. For the first time, the oxygen-repairing efficiency on MoS2 monolayers at atomic scale is quantitatively evaluated. The sulfur defect density is greatly reduced from (2.71 ± 0.65) × 1013 down to (4.28 ± 0.27) × 1012 cm-2, which is one order of magnitude lower than reported as-grown MoS2. Such prominent defect deduction is owing to the kinetically more favorable configuration of oxygen substitution and an increase in sulfur vacancy formation energy around oxygen-incorporated sites by the first-principle calculations. Furthermore, the sulfur vacancies induced donor defect states is largely eliminated confirmed by quenched defect-related emission. The devices exhibit improved carrier mobility by more than three times up to 65.2 cm2 V-1 s-1 and lower Schottky barrier height reduced by half (less than 20 meV), originating from the suppressed Fermi-level pinning effect from disorder-induced gap state. The work provides aneffective route toward engineering the intrinsic defect density and electronic states through modulating synthesis kinetics of 2D materials.

Unlocking the impact of international financial support to infrastructure, energy efficiency, and ICT on CO2 emissions in India

Financial resource constraints prevent developing nations from investing in the infrastructure needed for the green transition. For this reason, it is well known that numerous financial aid programs are offered globally, mainly to wealthy developing nations whose economies are predicated on high energy consumption. It hasn't been looked into if these resources are allocated to worthwhile projects. This study examines how foreign financial assistance in this area affects India's infrastructure emissions. The effects of natural resources, economic growth, information and communication technology, energy efficiency (oil and gas), and natural resources on the environment are being investigated as well. The novel multivariate quantile on-quantile regression technique is used in this context to examine a time-series data set spanning 2000–2021. According to the findings, there is a correlation between reduced carbon emissions and increased foreign financial aid. Likewise, advancements in energy efficiency and information and communication technologies also benefit the ecosystem. However, India's emissions are rising due to its abundant natural resources and economic expansion. Policy recommendations were made regarding the need for India to use international financial aid primarily to strengthen environmentally friendly infrastructure rather than solving problems such as current account deficit or budget deficit.

Impact of halogens modifications on physical characteristics of lead-free hybrid double perovskites compounds Cs2YCuX6 (X=Cl, Br, and I) for energy storage applications: First principles investigations

The purpose of this study is to examine the structural, electronic, optical, and thermoelectric features of novel double perovskite Cs2YCuX6 (X=Cl, Br, and I) for the first time in order to look for potential applications in solar power systems. Using first-principles calculations based on the widely recognized Density Functional Theory (DFT) and the PBE-Generalized Gradient Approximation (GGA) functional included in the WEIN2k package, the characteristics of the perovskites were determined. From the results of band structure and Total Density of States (TDOS) the energy band gap of Cs2YCuCl6, Cs2YCuBr6, and Cs2YCuI6 are observed 2.34 eV, 2.03 eV and 1.68 eV respectively. The PDOS outcomes shows that the formation of the valance and conduction bands is due to the hybridization of Cu-3d and halogen ions such that (X=Cl, Br, and I). The calculated values of goldsmith’s tolerance factor and formation energy reveal that the examined halide perovskites are structurally and thermodynamically stable. The electron localization function ELF and bader charge analysis show that the ionic nature between Cs and halogen ions X. Regarding the optical behavior, Cs2YCuI6has shown maximum absorption of electromagnetic radiation and conductivity in the ultraviolet and visible region i.e. (128–471 nm) which makes it a suitable candidate for optoelectronic and solar cell applications. The thermoelectric properties of the studied compounds have been calculated by means of the Boltztrap code. The presented findings unveil that amongst all studied compoundsCs2YCuI6 is best candidate for solar cell and thermoelectric applications due to higher conductivity, larger absorption range, significant Seebeck coefficient and higher Power factor.

Powering Growth: The Dynamic Impact of Renewable Energy on GDP in ASEAN-5

This study investigates the dynamic relationships between renewable energy consumption, labor force, gross fixed capital (GFC), and GDP across ASEAN-5 nations from 1984 to 2020. Utilizing data from the World Development Indicators (WDI), the Energy Information Agency (EIA), and national labor statistics, we employ unit root tests, ARDL bound testing for cointegration, and Toda-Yamamoto causality procedures. Our findings indicate significant long-term cointegration between the studied variables in Indonesia and the Philippines, suggesting persistent economic relationships, while results for Malaysia show no cointegration and remain inconclusive for Thailand. The economic analysis reveals that GFC robustly drives GDP growth across these countries, whereas the impacts from labor force and renewable energy consumption are more variable. Causality tests further demonstrate that renewable energy consumption significantly fosters GDP growth in Indonesia, Malaysia, and Singapore, aligning with the growth hypothesis. Conversely, findings for the Philippines and Thailand support the neutrality hypothesis, indicating no direct causal impacts. These insights underline the crucial role of tailored renewable energy strategies to enhance economic growth and sustainability in ASEAN-5, providing valuable policy implications for regional energy governance.

Addressing accuracy by prescribing precision: Bayesian error estimation of point defect energetics

With density functional theory (DFT), it is possible to calculate the formation energy of charged point defects and in turn to predict a range of experimentally relevant quantities, such as defect concentrations, charge transition levels, or recombination rates. While prior efforts have led to marked improvements in the accuracy of such calculations, comparatively modest effort has been directed at quantifying their uncertainties. However, in the broader DFT research space, the development of Bayesian Error Estimation Functionals (BEEF) has enabled uncertainty quantification (UQ) for other properties. In this paper, we investigate the utility of BEEF as a tool for UQ of defect formation energies. We build a pipeline for propagating BEEF energies through a formation-energy calculation and test it on intrinsic defects in several materials systems spanning a variety of chemistries, bandgaps, and crystal structures, comparing to prior published results where available. We also assess the impact of aligning to a deep-level transition rather than to the VBM (valence band maximum). We observe negligible dependence of the estimated uncertainty upon a supercell size, though the relationship may be obfuscated by the fact that finite-size corrections cannot be computed separately for each member of the BEEF ensemble. Additionally, we find an increase in estimated uncertainty with respect to the absolute charge of a defect and the relaxation around the defect site without deep-level alignment, but this trend is absent when the alignment is applied. While further investigation is warranted, our results suggest that BEEF could be a useful method for UQ in defect calculations.

Systematic investigation of physical properties of Mg3XO4 (X = Cr, Mn, Fe, Co, Ni); a computational approach

Material development is primarily dependent on their design and theoretical exploration. Density functional theory is a great tool to achieve this goal. Here, Mg3XO4 (X = Cr, Mn, Fe, Co, Ni) are considered in order to reveal their full characteristics using density functional theory. Mg3XO4 (X = Cr, Mn, Fe, Co, Ni) are investigated in terms of their structural, elastic, mechanical, thermodynamic, electronic, and dynamic properties. The formation energies for Mg3XO4 (X = Cr, Mn, Fe, Co, Ni) are found to be negative implying synthesisability and dynamic stability of these materials. The evolution of elastic constants of materials demonstrates that all materials satisfy the Born stability criterion, hence Mg3XO4 (X = Cr, Mn, Fe, Co, Ni) are mechanically stable. Several polycrystalline parameters are derived by using elastic constants and evaluated. All materials are found be brittle, hard (Vickers hardness) and magnetic. They exhibit some degree of anisotropy in Young/Shear modulus and Poisson’s ratio. The electronic band structures for Mg3CrO4, Mg3MnO4 and Mg3FeO4 indicated a semi-metallic nature whereas for Mg3CoO4 and Mg3NiO4 indicated metallic nature because both the majority and minority energy bands cut the Fermi level. The phonon modes are found to be in positive frequencies that confirms dynamical stability. The materials’ free energy, entropy, specific heat capacity, Debye and melting temperatures, minimum thermal conductivity and Grüneisen parameters are also obtained and discussed.

Stability and Electronic Properties of K‐Sb and Na‐Sb Binary Crystals from High‐Throughput Ab Initio Calculations

AbstractThe study of the fundamental properties of alkali antimonide photocathodes for particle accelerators is currently hindered by the limited purity of the samples. First‐principles studies can effectively complement experiments to gain insight into the stability and the electronic structure of these compounds. In this high‐throughput analysis based on density‐functional theory (DFT), two families of binary crystals with K‐Sb and Na‐Sb compositions expected to form during evaporation of multi‐alkali antimonide photocathodes are investigated. Starting from an initial pool of structures mined from existing computational databases, automatized routines included in the in‐house developed library aim2dat are employed to determine the stability and the electronic properties of the aforementioned systems. By analyzing the formation energy, the structures are ranked in a convex hull retaining the information of their crystalline arrangement. Next, the band structure and the projected density of states of selected stable compounds are analyzed. Adopting the r2SCAN functional for the DFT calculations, reliable estimates of the character and size of the bandgaps are obtained and discussed in relation to the relative alkali content in the crystals. These results provide useful indications to predict and characterize binary phases forming during the growth of multi‐alkali antimonide photocathodes.

Toward Controllable Self‐Reduction of Mn4+ to Mn2+ by Lanthanide Ions for Luminescence Based Colorimetric Sensing of Temperature

AbstractLuminescence intensity ratio (LIR) based optical thermometers have attracted lots of attention. In case of color tunable luminescence with the variation of LIR, “RGB colorimetry” based on convenient temperature sensing using a smartphone or digital camera is available. However, narrow emission bands with primary colors are needed for avoiding color crosstalk and achieving high sensitivities. In this paper, Mn4+ and Mn2+ coactivated CaAl12O19 (CAO) phosphors are reported that show a narrow red emission of Mn4+ and green one of Mn2+ with the number of the two ions controlled by lanthanide ions through manipulation of self‐reduction of Mn4+ to Mn2+ in air. The self‐reduction in CAO via the addition of Ce4+ is mainly studied. First‐principles calculation shows that the self‐reduction is driven by Ca vacancies that are produced in aliovalent substitution of Ce4+ for Ca2+ and can reduce the formation energy of Mn2+. The comparative study of temperature sensing based on LIR and RG colorimetry is conducted. The relative sensitivity based on LIR is high as 4.5% K−1 at 373 K and that for RG colorimetry can reach 2% K−1 at 350 K. These findings provide a strategy for manipulation of manganese valance states and a phosphor for RG colorimetry temperature sensing.

Unveiling the energy driven potential Sc-based double perovskite through comprehensive DFT screening on physical, optoelectronic and transport characteristic of Sr2ScAsO6 compound

Recently, double perovskites have been emerged as promising candidates due to their enthralling electronic as well as thermoelectric properties. In our present investigation, we have made a systematic effort to evaluate the optical properties along with elastic, mechanical and thermoelectric properties of Sr2ScAsO6 using DFT tactics as implemented with WIEN2k code. The exchange - correlation potential has been treated with various approximations like LDA, PBE-GGA, WC-GGA and PBE-sol GGA. The formation energy, cohesive energy and tolerance factor have been computed for the studied double perovskite to confirm its thermodynamic as well as structural stability in the cubic phase. The ductility as well as brittleness of the compound have been checked by evaluating the B/GH and Poisson's ratios. The value of band gap is found to be 2.147 eV with PBE-GGA + TB-mBJ method, which is the accurate mode of band gap computations. The spin-orbit coupling effect and its exclusion were considered during the calculations. The temperature and pressure dependency of thermodynamic properties have been studied with the aid of modified-Gibbs2 model. The thermoelectric behaviour of the studied double perovskite has been explored and found to hold a power factor of 12.2 × 1012 W m−1 K−2 s−1 at 1200 K. As these compositions have high room temperature figure of merit values and recorded values of 0.035, they are also suitable for application in thermoelectric devices.

Zn-substituted Co3O4 crystal anchored on porous carbon nanofibers for high performance supercapacitors

Metal-organic frameworks (MOFs) are a promising class of electrode materials for supercapacitors. In this work, MOF-derived transition metal oxide/carbon nanofiber composites (ZnCoO/C) are synthesized through a freeze-drying method followed by a carbonization process. The crystal structure of the ZnCoO/C product is regulated by changing the ratio of Co to Zn, which in turn influences its electrode properties. The electrochemical tests reveal that the ZnCoO/C-2 electrode demonstrates an impressive specific capacitance of 356.3 F g-1 at 1 A g-1 and maintains a capacitance retention exceeding 77 % after 10,000 cycles, which exhibits a good cycling stability. It is found that appropriate Zn substitution can diminish the crystallinity of the material, augment the active sites, and enhance the specific capacitance of the electrode material. Considering the heteroatom substitution tends to introduce vacancy defects in the crystals, this work theoretically explores the effect of oxygen vacancies on the electrode materials. As the oxygen vacancy concentration increases, the band gap and the adsorption energy of the models decrease; conversely, the formation energy of the models shows an increasing tendency. This indicates that an increase in oxygen vacancies can enhance the electrical conductivity of electrode materials and facilitate their kinetic process but destroy the stability of crystal. This research explores the interplay between the microstructure and the electrochemical performance of electrode materials, providing a foundational reference for the design of structurally optimized high-performance electrodes and further elucidating the energy storage mechanisms in supercapacitors.

Stable crystal structure prediction using machine learning-based formation energy and empirical potential function

Crystal structure prediction aims to predict stable and easily experimentally synthesized materials, which accelerates the discovery of new materials. It is worth noting that the stability of materials is the basis for ensuring high performance and reliable application of materials. Among which, the thermodynamic and molecular dynamics stability is especially important. Therefore, this paper proposes a method to predict stable crystal structures using formation energy and Lennard-Jones potential as evaluation indicators. Specifically, we use graph neural network models to predict the formation energy of crystals, and employ empirical formulas to calculate the Lennard-Jones potential. Then, we apply Bayesian optimization algorithms to search for crystal structures with low formation energy and Lennard-Jones potential approaching zero, in order to ensure the thermodynamic stability and dynamics stability of materials. In addition, considering the impact of the bonding situation between atoms in the crystal on the structural stability, this article uses contact map to analyze the atomic bonding situation of each crystal to screen out more stable materials. Finally, the experimental results show that the method we proposed can not only reduce the time for crystal structure prediction, but also ensure the stability of crystal materials.

A first-principles study on structural stability and magnetoelectric coupling of two-dimensional BaTiO3 ultrathin film with Cr and Cu substituting Ti site

A study on Jahn–Teller distortion reveals that the configuration with Ti-substitution is more stable than that in the case of Ba-replacement. However, magnetoelectric coupling is weak as no spontaneous polarization is formed in the doped unit cell. Taking the atomic radius, low price, and electronegativity into account, Cu was selected to replace Ti together with Cr. Formation energy and phonon spectrum show structural stability. The spontaneous polarization was calculated to be 0.110, 0.114, and 0.247 and 8.078, 0.288, and 0.255 μC/cm2, respectively, in the Cr- and Cu-doped unit cell, corresponding to the directions [100], [010], and [001]. With the application of electric fields, the total magnetic moment was generally enhanced, which resulted in a strong magnetoelectric coupling. In addition, the corresponding coefficient is more than 10 V/cmOe, indicating that the modified BaTiO3 may be a good candidate for single-phase multiferroics. Clearly, co-doping with nonferromagnetic and nonmagnetic elements increases the diversity of new multiferroics.

Theoretical investigation of Cu influence on the stability characteristics of T-phase in crossover alloys

Abstract In crossover Al-Mg-Zn alloys, the T-phase (Mg32(Al, Zn)49) is crucial for reinforcement. The critical nucleation size of the precipitated T-phase is notably reduced by Cu addition, as well as the activation energy. There is a lack of theoretical research on the influence of Cu elements on the stability of T-phases and mechanical properties. In this work, we systematically investigate the influence of varying Cu concentration on the T-phases by examining their stability, mechanical properties, and electronic structure characteristics through first-principles calculations. The findings reveal that the T-phase maintains lattice stability within the 0 to 5% Cu content range, with a linear decrease in the lattice parameter and formation energy (–0.16 ~ –0.15 eV/atom). Additionally, there is an observable positive correlation trend between the elastic moduli (B, E, and G) of the T-type phase and the Cu content. It is shown that the T-phase exhibits inherent ductility. Analysis based on Pugh’s criterion and Poisson’s ratio indicates a reduction in the ductility with increasing Cu content in the T-phase. This work theoretically validates the previous experimental observations and reveals the impacts of Cu concentration on the T-phase.

First-principles investigation of structural, electronic, optical and thermoelectric performance of stable inorganic double perovskites A2AlAgBr6 (A=K, Rb, Cs) for energy harvesting

In this work, the structural, electronic, optical and thermoelectric properties of Cs2AlAgBr6, K2AlAgBr6 and Rb2AlAgBr6 have been investigated using WIEN2k code. All the three double perovskites show stability. The stability is confirmed by calculating their formation energy, tolerance factor and molecular dynamic simulations. The electronic properties revealed the understudy compounds as semiconductors of direct band gap of 2.62, 2.61 and 2.59 eV for Cs2AlAgBr6, K2AlAgBr6 and Rb2AlAgBr6, respectively. The absorption band of our compounds is mostly in the ultraviolet energy range which is particularly significant for optoelectronic devices. The studied double perovskites exhibit a large Seebeck coefficient and electrical conductivity, which is significant for the high figure of merit. These properties make them particularly suitable for thermoelectric (TE) devices and other photovoltaic applications, as their high figure of merit at low temperatures opens up new possibilities for these materials.

Revealing elastic, thermophysical, optoelectronic, and transport characteristics of halide double perovskites Na2TlSbZ6 (Z = Cl/Br/I) for eco-friendly technologies: DFT analysis

Halide double perovskites (HDPs) exhibit advantageous functional characteristics, making them extremely suitable for utilization in photovoltaics and thermoelectrics. The current investigation utilized the WIEN2k simulation code, which is based on the principle of density functional theory (DFT), to analyze the structural, elastic, thermophysical, electro-optic, and transport properties of Na2TlSbZ6 (Z = Cl/Br/I). The cubic phase and chemical stability have been verified by calculating the tolerance factor and formation energy. The elastic features that exhibit flexibility, ductility, and mechanical stability for studied HDPs have been demonstrated. Three-dimensional Young’s modulus plots confirm the anisotropy in all examined HDPs. The electronic characteristics have been estimated to determine the band gap and details regarding the distribution of electronic states across bands. The band gap values of examined HDPs ranging between 1.40 and 0.78 eV confirm their semiconductor nature. The optical attributes, including dielectric function, absorption, reflectivity, and loss function, have been studied in detail. The reported optical absorption spectrum indicates that Na2TlSbZ6 (Z = Cl/Br/I) perovskites can be utilized in optoelectronic and solar energy technologies. Transport parameters have been comprehensively elucidated to predict the thermal energy conversion capability. The anticipated merit values of 0.84, 0.88, and 0.92 at room temperature validate their higher thermoelectric response for technological applications. These theoretical findings indicate the significant potential of these HDPs for solar cells and thermoelectric devices.

Exploring the structural, electronic, mechanical, magnetic and optical properties of Cs-based hydride-perovskites CsXH3 (X = Cr, Mn) for hydrogen storage application

Low cast hydride-perovskites are more efficient in power conversion and for energy storage. Here in, structural investigation, electronic, mechanical and optical properties of hydrogen based CsXH3 (X = Cr, Mn) compounds using the density functional theory. The result shows that both materials crystallize into cubic structure. The thermodynamic and dynamic stabilities are conformed through formation energy and phonon dispersion curve. The optimized lattice constants are 3.52 Å and 3.54 Å for CsCrH3 and CsMnH3 respectively. Both materials are found to be half metallic in nature. IR-Elast package are used to obtain elastic constants. The elastic study presents that both materials are ductile and have anisotropic nature. The optical parameters are studied in the range of 0–10 eV. The optical results show that both materials have an excellent optical absorption. The values obtained of gravimetric hydrogen storage capacity for these compounds are 1.55 % and 1.58 % for CsMnH3 and CsCrH3 respectively indicating that these materials can be an excellent candidate for hydrogen energy storage.

CO2 and NO2 formation on amorphous solid water

Context. The dynamics of molecule formation, relaxation, diffusion, and desorption on amorphous solid water (ASW) is studied in a quantitative fashion. Aims. The formation probability, stabilization, energy relaxation, and diffusion dynamics of CO2 and NO2 on cold ASW following atom+diatom recombination reactions are characterized quantitatively. Methods. Accurate machine-learned energy functions combined with fluctuating charge models were used to investigate the diffusion, interactions, and recombination dynamics of atomic oxygen with CO and NO on ASW. Energy relaxation to the ASW and into water internal degrees of freedom were determined from the analysis of the vibrational density of states. The surface diffusion and desorption energetics were investigated with extended and nonequilibrium MD simulations. Results. The reaction probability is determined quantitatively and it is demonstrated that surface diffusion of the reactants on the nanosecond time scale leads to recombination for initial separations of up to 20 Å. After recombination, both CO2 and NO2 stabilize by energy transfer to water internal and surface phonon modes on the picosecond timescale. The average diffusion barriers and desorption energies agree with those reported from experiments, which validates the energy functions. After recombination, the triatomic products diffuse easily, which contrasts with the equilibrium situation, in which both CO2 and NO2 are stationary on the multinanosecond timescale.