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The reaction mechanisms and corresponding structure-activity relationships of tertiary amines with respect to CO2 capture have been investigated using density functional theory (DFT) calculations. The reaction mechanism for CO2 capture via base-catalyzed hydration to form bicarbonate is proposed to proceed in a single step involving proton transfer and the formation of a carbon-oxygen bond. Based on the height of the reaction barriers, we suggest that amines containing side chains with the ethyl group, along with a single hydroxyl group, and cyclic structures, are especially active for CO2 capture. The activation barrier is shown to be a descriptor for predicting the experimental CO2 loading values. To enhance the prediction accuracy for CO2 loading, we employ the sure-independence screening and sparsifying operator (SISSO) method, which can scan a large pool of mathematical terms stemming from combining DFT-derived descriptors to select the superior ones. Thus, we can predict the CO2 loading with acceptable accuracy from the obtained mathematical expression. Since the computational workload of applying this expression is negligible, this facilitates high-throughput screening and accelerates the design of tertiary amines for CO2 capture., (© 2024 Wiley‐VCH GmbH.)

We present a new general-purpose machine learning model that is able to predict a variety of crystal properties, including Fermi level energy and band gap, as well as spectral ones such as electronic densities of states. The model is based on atomic representations that enable it to effectively capture complex information about each atom and its surrounding environment in a crystal. The accuracy achieved for band gaps exceeds results previously published. By design, our model is not restricted to the electronic properties discussed here but can be extended to fit diverse chemical descriptors. Its advantages are (a) its low computational requirements, making it an efficient tool for high-throughput screening of materials; and (b) the simplicity and flexibility of its architecture, facilitating implementation and interpretation, especially for researchers in the field of computational chemistry.

High-accuracy molecular force field models suited for hot gases and plasmas are not as abundant as those geared toward ambient pressure and temperature conditions. Here, we present an improved version of our previous electron-density based force field model that can now account for polarization effects by adjusting the atomic valence electron contributions to match ab initio calculated Mulliken partial charges. Using a slightly modified version of the Hohenberg-Kohn theorem, we also include an improved theoretical formulation of our model when applied to systems with degenerate ground states. We present two variants of our polarizable model, fitted from ab initio reference data calculated at CCSD(T)/cc-pVTZ and CCSD(T)/CEP-31G levels of theory, that both accurately model water dimer interaction energies. Further improvements include the additional interaction components with fictitious non-spherically symmetric, yet atom-centered, electron densities and fitting the exchange and correlation coefficients against analytical expressions. The latter removes all unphysical oscillations that are observed in the previous non-polarizable variant of our force field., (© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).)

The conversion of chemically modified biomass into more valuable chemicals has recently gained significant attention from industry. In this study, we investigate the adsorption of fructose and its conversion into two trioses, glyceraldehyde (GLA) and dihydroxyacetone (DHA), on metal-organic frameworks using density functional theory calculations. The reaction mechanism proceeds through two main steps: first, the opening of the fructose ring; second, the retro-aldol fragmentation, which is favored over intramolecular hydrogen shifts. The substitution of a tetravalent metal in the metal-organic framework leads to different adsorption strengths in the order Hf-NU-1000 > Zr-NU-1000 > Ti-NU-1000. The catalytic activities of Hf-NU-1000 and Zr-NU-1000 are found to be similar. Both are more active than Ti-NU1000, corresponding to their relative Lewis acidity. It was found that functionalization of the organic linkers of the Hf-NU-1000 MOF does not improve its catalytic activity. The catalytic activity follows the order Hf-MOF-808 > Hf-NU-1000 > Hf-UIO-66 when based on either the overall activation energy or the turnover frequency (TOF).

In high-energy molecular dynamics or Monte Carlo simulations, standard force fields optimized for simulations at ambient temperatures are inadequate. This is largely because their repulsive parts have been regarded as not very significant, even well below zero interaction energies. It is, therefore, not obvious which force fields to resort to for simulating hot gases or plasmas. A force field model that uses the electronic densities of noninteracting atoms or molecules within the pair approximation is introduced. We start by deriving a naïve model that neglects any exchange and correlation effects between the electronic clouds and then correct this model by adding a term calibrated from ab initio calculations using the CCSD(T)/cc-pVTZ level of theory. The resulting expression for this term can be regarded as a simple exchange-correlation function. We compare the results for the repulsive part of the potential energy hypersurfaces with the force fields commonly used on some dimers of small molecules.

Density-based topology optimization is used to design large-scale, multi-layer grating couplers that comply with commercial foundry fabrication constraints while simultaneously providing beam profiles that efficiently couple to a single-mode optical fiber without additional optics. Specifically, we describe the design process and experimentally demonstrate both single- and dual-polarization grating couplers that couple at normal incidence (0° from the normal) with low backreflections (-13.7 dB and -15.4 dB at the center wavelength), broad 3 dB bandwidths (75 nm and 89 nm), and standard coupling efficiencies (-4.7 dB and -7.0 dB). The dual-polarization grating couplers exhibit over 30 dB of polarization extinction across the entire band. The devices were fabricated on the GlobalFoundries 45CLO CMOS platform and characterized across three separate wafers. This new design approach produces distinct features for multiple foundry layers and yields emitters with arbitrary, user-specified far-field profiles.

The geometrical effect of chlorine atom positions in polyatomic molecules after capturing a low-energy electron is shown to be a prevalent mechanism yielding Cl 2 - . In this work, we investigated hexachlorobenzene reduction in electron transfer experiments to determine the role of chlorine atom positions around the aromatic ring, and compared our results with those using ortho -, meta - and para -dichlorobenzene molecules. This was achieved by combining gas-phase experiments to determine the reaction threshold by means of mass spectrometry together with quantum chemical calculations. We also observed that Cl 2 - formation can only occur in 1,2-C 6 H 4 Cl 2 , where the two closest C-Cl bonds are cleaved while the chlorine atoms are brought together within the ring framework due to excess energy dissipation. These results show that a strong coupling between electronic and C-Cl bending motion is responsible for a positional isomeric effect, where molecular recognition is a determining factor in chlorine anion formation.

We present the electron-impact ionization cross sections (EICSs) of iron and chromium hydrides, nitrides, and oxides. The motivation of this work stems from the fact that chemical sputtering from a steel surface exposed to a hot plasma can create these molecules which in turn influence the composition and energy balance of the plasma. The latter influence is quantified by the EICS which we derive by using two semi-empirical methods which can be employed in the relevant energy range of 10-1000 eV. They are important molecular properties for plasma- and materials science. We discuss the foundations of the methods and present the cross sections of the high- and low-spin states of the species in their neutral ground states and of their cations., (Creative Commons Attribution license.)

Lithium-sulfur batteries (LSBs) are promising energy storage devices because of their high theoretical capacity and energy density. However, the "shuttle" effect in lithium polysulfides (LiPSs) is an unresolved issue that can hinder their practical commercial application. Research on LSBs has focused on finding appropriate materials that suppress this effect by efficiently anchoring the LiPSs intermediates. Quantum chemical computations are a useful tool for understanding the mechanistic details of chemical interaction involving LiPSs, and they can also offer strategies for the rational design of LiPSs anchoring materials. In this perspective, we highlight computational and theoretical work performed on this topic. This includes elucidating and characterizing the adsorption mechanisms, and the dominant types of interactions, and summarizing the binding energies of LiPSs on anchoring materials. We also give examples and discuss the potential of descriptors and machine learning approaches to predict the adsorption strength and reactivity of materials. We believe that both approaches will become indispensable in modelling future LSBs.

Dehydration reactions are important in the petroleum and petrochemical industries, especially for the feedstock production. In this work, the catalytic activity of zeolites with different acidities for the dehydration of ethanol to ethylene and diethylether is investigated by density functional calculations on cluster models of three isomorphous B, Al, and Ga substituted H-ZSM-5 zeolites. Both unimolecular and bimolecular mechanisms are investigated. Detailed reaction profiles for the dehydration reaction, assuming either a stepwise or a concerted mechanism, were calculated by using the ONIOM(MP2:M06-2X) + SCREEP method. The adsorption energies of ethanol are -21.6, -28.1, and -27.7 kcal mol -1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the rate-determining step of the unimolecular concerted mechanism for the ethylene formation are 48.5, 42.6, and 43.6 kcal mol -1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the ethoxy formation as the rate-determining step for the bimolecular formation of diethylether are 42.3, 40.0, and 41.1 kcal mol -1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The results indicate that the catalytic activities for the dehydration of ethanol decrease in the order H-[Al]-ZSM-5 ~ H-[Ga]-ZSM-5 > H-[B]-ZSM-5. Besides the acid strength, the zeolite framework affects the reaction by stabilizing the reaction intermediates, leading to more stable adsorption complexes and lower activation barriers., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Tirapazamine (TP) has been shown to enhance the cytotoxic effects of ionizing radiation in hypoxic cells, thus making it a candidate for a radiosensitizer. This selective behavior is often directly linked to the abundance of O 2 . In this paper, we study the electronic properties of TP in vacuum, micro-hydrated from one up to three molecules of water and embedded in a continuum of water. We discuss electron affinities, charge distribution, and bond dissociation energies of TP, and find that these properties do not change significantly upon hydration. In agreement with its large electron affinity, and bond breaking triggered by electron attachment requires energies higher than 2.5 eV, ruling out the direct formation of bioactive TP radicals. Our results suggest, therefore, that the selective behavior of TP cannot be explained by a one-electron reduction from a neighboring O 2 molecule. Alternatively, we propose that TP's hypoxic selectivity could be a consequence of O 2 scavenging hydrogen radicals.

Purpose: Right ventricular (RV) dysfunction in acute pulmonary embolism (PE) is a critical determinant of outcome. Obstructive sleep apnea (OSA) is a common comorbidity of PE and might also affect RV function. Therefore, we sought to investigate RV dysfunction in PE patients in proportion to the severity of OSA by evaluating the right-to-left ventricular (RV/LV) diameter ratio on computed tomographic pulmonary angiography (CTPA)., Materials and Methods: 197 PE patients were evaluated for sleep-disordered breathing by portable monitoring and nocturnal polysomnography. RV dilatation was defined as an RV/LV diameter ratio of ⩾ 1.0., Results: RV dilatation was significantly more frequent in OSA patients compared to study participants without OSA (66.4% vs 49.1%, P = .036). Elevated troponin I values, indicating myocardial injury due to acute, PE-related RV strain, were significantly more frequent in OSA patients with an apnea-hypopnea index (AHI) ⩾ 15/h compared to those with an AHI < 15/h (62.1% vs 45.8%, P = .035). However, RV dysfunction documented by the RV/LV diameter ratio on CTPA was not significantly associated with the severity of OSA in multivariable regression analysis., Conclusion: Patients with moderate or severe OSA might compensate acute, PE-related RV strain better, as they are adapted to repetitive right heart pressure overloads during sleep., Competing Interests: Declaration of conflicting interests:The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2020.)

The area used for mineral extraction is a key indicator for understanding and mitigating the environmental impacts caused by the extractive sector. To date, worldwide data products on mineral extraction do not report the area used by mining activities. In this paper, we contribute to filling this gap by presenting a new data set of mining extents derived by visual interpretation of satellite images. We delineated mining areas within a 10 km buffer from the approximate geographical coordinates of more than six thousand active mining sites across the globe. The result is a global-scale data set consisting of 21,060 polygons that add up to 57,277 km 2 . The polygons cover all mining above-ground features that could be identified from the satellite images, including open cuts, tailings dams, waste rock dumps, water ponds, and processing infrastructure. The data set is available for download from https://doi.org/10.1594/PANGAEA.910894 and visualization at www.fineprint.global/viewer .

The conversion of ethanol to more valuable hydrocarbon compounds receives great attention in chemical industries because it could diminish the dependency on petroleum as raw material. We investigate the catalytic performance of Fe-supported MOF NU-1000 for the dehydrogenation of ethanol to acetaldehyde with nitrous oxide (N2O) by deriving the relevant reaction profiles with density functional theory calculations. In the proposed mechanism, the activation barrier of the rate-determining step is almost four times lower in the presence of N2O than without it. The supported NU-1000 framework plays also important role since it facilitates electron transfers and stabilizes all species along the reaction coordinate. When considering the catalytic activity of tetravalent metal centers (Zr, Hf and Ti) substituted into NU-1000 it is found that their activity decreases in the order Hf ≥ Zr > Ti, based on activation energies and turnover frequencies (TOF). Concerning MOF linkers, we show that the catalytic activity is not further improved by functionalizing NU-1000 with either electron-donating or electron-withdrawing organic groups.

Machine learning approaches have been successfully employed in many fields of computational chemistry and physics. However, atomistic simulations driven by machine-learned forces are still very challenging. Here we show that reactive self-sputtering from a beryllium surface can be simulated using neural network trained forces with an accuracy that rivals or exceeds other approaches. The key in machine learning from density functional theory calculations is a well-balanced and complete training set of energies and forces. We have implemented a refinement protocol that corrects the low extrapolation capabilities of neural networks by iteratively checking and improving the molecular dynamic simulations. The sputtering yield obtained for incident energies below 100 eV agrees perfectly with results from ab initio molecular dynamics simulations and compares well with earlier calculations based on pair potentials and bond-order potentials. This approach enables simulation times, sizes and statistics similar to what is accessible by conventional force fields and reaching beyond what is possible with direct ab initio molecular dynamics. We observed that a potential fitted to one surface, Be(0001), has to be augmented with training data for another surface, Be(011̄0), in order to be used for both., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Introduction: Obstructive sleep apnea (OSA) may have prothrombotic effects., Objective: To investigate the effect of OSA on disease severity, pulmonary artery thrombus load, and prognosis in patients with acute pulmonary embolism (PE)., Methods: In 101 PE patients, disease severity was determined by the simplified PE severity index (sPESI) score, pulmonary artery thrombus load was quantified by the pulmonary artery obstruction index (PAOI), and sleep-disordered breathing was evaluated by nocturnal polygraphy., Results: Obstructive sleep apnea patients with an apnea-hypopnea index (AHI) ≥ 15/h cohort were significantly older (p < 0.001) and had significantly lower oxygen saturations (p = 0.008) when acute PE was diagnosed. The sPESI scores (p < 0.001), the PAOI (p = 0.005) and the N-terminal pro-brain-type natriuretic peptide (NT-proBNP) values (p = 0.009), were significantly higher in the AHI ≥ 15/h subgroup. In a multivariate regression analysis, the AHI remains a significant predictor for sPESI scores ≥ 1 (p = 0.003), increased NT-proBNP levels (p = 0.047), and elevated PAOI (p = 0.032). During the median follow-up time of 53 (interquartile range 38-70) months, all-cause and cardiovascular-related mortality was significantly higher in the AHI ≥ 15/h cohort (p = 0.004 and p = 0.015, respectively)., Conclusions: Obstructive sleep apnea is associated with pulmonary artery thrombus load, disease severity, and survival in acute PE possibly due to its prothrombotic effects.

We investigate the tautomerization of phenol catalyzed by acid-base active pair sites in Lewis acidic Beta zeolites by means of density functional calculations using the M06-L functional. An analysis of the catalytic mechanism shows that hafnium on the Beta zeolite causes the strongest absorption of phenol compared to zirconium, tin, and germanium. This can be rationalized by the highest delocalization of electron density between the Lewis site and the oxygen of phenol which can in turn be quantified by the perturbative E (2) stabilization energy. The reaction is assumed to proceed in two steps, the phenol O-H bond dissociation and the protonation of the intermediate to form the cyclohexa-2,4-dien-1-one product. The rate determining step is the first one with a free activation energy of 26.3, 25.0, 22.1 and 22.7 kcal mol -1 for Ge-Beta, Sn-Beta, Zr-Beta, and Hf-Beta zeolites, respectively. The turnover frequencies follow these reaction barriers. Hence, the intrinsic catalytic activity of the Lewis acidic Beta zeolites studied here is in the order of Hf-Beta≈Zr-Beta>Sn-Beta> Ge-Beta for the tautomerization of phenol., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The carbonyl-ene reaction between encapsulated formaldehyde and propylene over the coordinatively unsaturated metal-organic frameworks M3(btc)2 (M = Fe, Co, Ni, Cu and Zn) has been investigated by means of density functional calculations. Zn3(btc)2 adsorbs formaldehyde strongest due to electron delocalization between Zn and the oxygen atom of the reactant molecule. The reaction is proposed to proceed in a single step involving proton transfer and carbon-carbon bond formation. We find the relative catalytic activity to be Zn3(btc)2 > Fe3(btc)2 ≥ Co3(btc)2 > Ni3(btc)2 > Cu3(btc)2, based on activation energy and turnover frequencies (TOF). The low activation energy for Zn3(btc)2 compared to the others can be explained by the delocalization of electron density between the carbonyl bond and the catalyst active sites, leading to a more stable transition state. The five MOFs are used to propose a descriptor for the relationship between activation energy on one side and electronic properties or adsorption energies on the other side in order to allow a quick screening of other catalytic materials for this reaction.

We report calculations of total (and absolute) electron-impact ionization cross sections (EICSs) for the fusion-relevant diatomic molecular species BeH, BeN, BeO, WH, WBe, WN, WO, O 2 , and N 2 by means of the Deutsch-Märk and the binary-encounter-Bethe methods in the energy range from threshold to 10 keV. In addition, we discuss an empirical scheme to estimate partial cross sections from the total ones based on reaction energetics and empirical threshold laws and explore its accuracy by assessing available experimental data on total and partial EICSs. Finally, we also report parameters obtained by fitting the calculated cross sections to an expression commonly used in fusion edge plasma modeling.

D-dimer might be correlated with prognosis in pulmonary embolism (PE). The predictive value of plasma D-dimer for disease severity and survival was investigated in the lowest and highest D-dimer quartile among 200 patients with PE. Patients with high D-dimers were significantly more often hypotensive ( P = .001), tachycardic ( P = .016), or hypoxemic ( P = .001). Pulmonary arterial obstruction index (PAOI) values were significantly higher in the high D-dimer quartile ( P < .001). Elevated troponin I (TNI) levels ( P < .001), simplified PE severity indices ≥1 ( P < .001), right-to-left ventricular (RV/LV) diameter ratios ≥1 ( P < .001), and thrombolysis ( P = .001) were more frequent in the high D-dimer quartile. D-dimer was associated with RV/LV ratios ≥1 ( P = .021), elevated PAOI ( P < .001) or TNI levels ( P < .001), hypotension ( P < .001), tachycardia ( P = .003), and hypoxemia ( P < .001), but not with long-term all-cause mortality. D-dimer predicts disease severity but not long-term prognosis in acute PE, possibly due to a more aggressive treatment strategy in severely affected patients.

We report total electron-impact ionisation cross sections (EICSs) of cisplatin, its hydrolysis products and transplatin in the energy range from threshold to 10 keV using the binary-encounter-Bethe (BEB) and its relativistic variant (RBEB), and the Deutsch-Märk (DM) methods. We find reasonable agreement between all three methods, and we also note that the RBEB and the BEB methods yield very similar (almost identical) results in the considered energy range. For cisplatin, the resulting EICSs yield cross section maxima of 22.09 × 10 -20  m 2 at 55.4 eV for the DM method and 18.67 × 10 -20  m 2 at 79.2 eV for the (R)BEB method(s). The EICSs of monoaquated cisplatin yield maxima of 12.54 × 10 -20  m 2 at 82.8 eV for the DM method and of 9.74 × 10 -20  m 2 at 106 eV for the (R)BEB method(s), diaquated cisplatin yields maxima of 7.56 × 10 -20  m 2 at 118.5 eV for the DM method and of 5.77 × 10 -20  m 2 at 136 eV for the (R)BEB method(s). Molecular geometry does not affect the resulting EICS significantly, which is also reflected in very similar EICSs of the cis - and trans -isomer. Limitations of the work as well as desirable future directions in the research area are discussed., (© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

Obstructive sleep apnea (OSA) might influence disease severity in acute pulmonary embolism (PE). 253 survivors of acute PE were evaluated for sleep-disordered breathing by portable monitoring and nocturnal polysomnography. PE patients with an apnea-hypopnoea index (AHI) ≥ 15/h were significantly older (p < 0.001), had significantly impaired renal (p < 0.001) and left ventricular functions (p = 0.003), showed significantly elevated troponin I (p = 0.005) and D-dimer levels (p = 0.024), were hospitalised significantly longer (p < 0.001), and had significantly elevated PE severity scores (p = 0.015). Moderate or severe OSA was significantly (p = 0.006) more frequent among intermediate- and high-risk PE patients (81.0%) compared to the low-risk PE cohort (16.3%). Multiple logistic regression analysis revealed that PE patients in the AHI ≥ 15/h cohort were at significant risk for myocardial injury (p = 0.015). Based on clinical risk stratification models, patients with no relevant OSA syndrome tended to be at a lower risk for short-term mortality (p = 0.068). Acute PE might present more severely in OSA patients, possibly due to nocturnal hypoxemia or OSA-related hypercoagulability.

The hydrogen transfer of furfural to furfuryl alcohol with i-propanol as the hydrogen source over cation-exchanged Lewis acidic BEA zeolite has been investigated by means of density functional calculations. The reaction proceeds in three steps. First the O-H bond of i-propanol is broken to form a propoxide intermediate. After that, the furylmethoxy intermediate is formed via hydrogen transfer process, and finally furylmethoxy abstracts the proton to form the furfuryl alcohol product. The second step is rate-determining by requiring the highest activation energy (23.8 kcal/mol) if the reaction takes place on Li-Sn-BEA zeolite. We find that the catalytic activity of various cation-exchanged Sn-BEA zeolites is in the order Li-Sn-BEA > Na-Sn-BEA > K-Sn-BEA. The lower activation energy for Li-Sn-BEA compared to Na-Sn-BEA and K-Sn-BEA can be explained by the larger charge transfer from the carbonyl bond to the catalyst, leading to its activation and to the attraction of the hydrogen being transferred. The larger charge transfer in turn is due to the smaller gap between the energies of furfural HOMO and the zeolite LUMO in Li-Sn-BEA, compared to both Na-Sn-BEA and K-Sn-BEA. In a similar way, we also compare the catalytic activity of tetravalent metal centers (Sn, Zr, and Hf) substituted into BEA and find in the order Zr ≥ Hf > Sn, based on activation energies. Finally we investigate statistically which property of the reactants is a suitable descriptor for an approximative prediction of the reaction rate in order to be able to quickly screen promising catalytic materials for this reaction.

The aerobic epoxidation of propylene over the metal-organic framework Fe 3 (btc) 2 (btc = 1,3,5-benzentricarboxylate) as catalyst has been investigated by means of density functional calculations. The mechanisms of the reaction towards propylene oxide, carbonylic products (acetone and propanal) and a pi-allyl radical were investigated to assess the efficiency of Fe 3 (btc) 2 for the selective formation of propylene oxide. Propylene oxide and carbonylic products are formed on Fe 3 (btc) 2 by proceeding via propyleneoxy intermediates in the first step. Subsequently, the intermediates can then either be transformed to propylene oxide by way of ring closure of the intermediate or to the carbonylic compounds of propanal and acetone via 1,2-hydride shift. The results show that the formation of propylene oxide is favored over the formation of carbonylic products mainly due to the activation barriers being 2-3 times smaller. The activation barriers for the formation of the propyleneoxy intermediates on the Fe 3 (btc) 2 catalyst for the first and second reaction cycle are also lower than the barriers obtained for the formation of the pi-allyl radical that acts as the precursor to combustion products. On the basis of these computational results, we therefore expect a high catalytic selectivity of the Fe 3 (btc) 2 catalyst with respect to the formation of propylene oxide. We also compared the catalytic activities of Fe 3 (btc) 2 and Cu 3 (btc) 2 . The activation energy of the rate-determining step is almost 2 times lower for Fe 3 (btc) 2 than that for Cu 3 (btc) 2 , due to a larger charge transfer from the catalytic site to the O 2 molecule in the case of Fe 3 (btc) 2 .

Dissociative electron attachment to three isomers of bromo-chlorotoluene was investigated in the electron energy range from 0 to 2 eV for gas temperatures in the range of 392-520 K using a crossed electron-molecular beam apparatus with a temperature regulated effusive molecular beam source. For all three molecules, both Cl - and Br - are formed. The ion yields of both halogenides show a pronounced temperature effect. In the case of Cl - and Br - , the influence of the gas temperature can be observed at the threshold peak close to 0 eV. The population of molecules that have some of their out-of-plane modes excited varies strongly in the temperature range investigated, indicating that such vibrations might play a role in the energy transfer towards bond breaking. Potential energy curves for the abstraction of Cl - and Br - were calculated and extrapolated into the metastable domain. The barriers in the diabatic curves approximated in this way agree well with the ones derived from the temperature dependence observed in the experiments.

The oxidation of CO by N 2 O over metal-organic framework (MOF) M 3 (btc) 2 (M = Fe, Cr, Co, Ni, Cu, and Zn) catalysts that contain coordinatively unsaturated sites has been investigated by means of density functional theory calculations. The reaction proceeds in two steps. First, the N-O bond of N 2 O is broken to form a metal oxo intermediate. Second, a CO molecule reacts with the oxygen atom of the metal oxo site, forming one C-O bond of CO 2 . The first step is a rate-determining step for both Cu 3 (btc) 2 and Fe 3 (btc) 2 , where it requires the highest activation energy (67.3 and 19.6 kcal/mol, respectively). The lower value for the iron compound compared to the copper one can be explained by the larger amount of electron density transferred from the catalytic site to the antibonding of N 2 O molecules. This, in turn, is due to the smaller gap between the highest occupied molecular orbital (HOMO) of the MOF and the lowest unoccupied molecular orbital (LUMO)  of N 2 O for Fe 3 (btc) 2 compared to Cu 3 (btc) 2 . The results indicate the important role of charge transfer for the N-O bond breaking in N 2 O. We computationally screened other MOF M 3 (btc) 2 (M = Cr, Fe, Co, Ni, Cu, and Zn) compounds in this respect and show some relationships between the activation energy and orbital properties like HOMO energies and the spin densities of the metals at the active sites of the MOFs.

Low-energy electrons effectively decompose the isomers 2-nitroimidazole and 4(5)-nitroimidazole by dissociative electron attachment (DEA) into a variety of fragment anions and radicals. The present study shows that a distinct selectivity for the two isomers occurs in the DEA reactions. Several new decay channels are observed for 2-nitroimidazole, including a dominant one leading to the loss of molecular H 2 O by attachment of a low-energy electron. In contrast, the loss of a single hydrogen atom is a much more efficient reaction in DEA to 4(5)-nitroimidazole. Quantum chemical calculations were carried out to explain the pronounced isomer effect found in the DEA experiment. Although the free energies of the reactions are similar for the different isomers, the very different natures of the dipole-bound states and valence-bound anions lead to preference for or hindrance of a particular dissociation channel. Nitroimidazolic compounds are considered as radiosensitizing compounds in tumor radiation therapy. The enhanced formation of fragments, including the highly reactive hydroxyl radical, in DEA to 2-nitroimidazole suggests that it may be a more efficient radiosensitizing agent than 4(5)-nitroimidazoles., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A proton-conducting coordination polymer of anionic one-dimensional (1D) chains of Zn 2+ phosphate and protonated imidazole with the formula of [Zn(HPO 4 )(H 2 PO 4 ) 2 ](ImH 2 ) 2 has been used as a novel supercapacitor material in aqueous electrolytes. This material stores charges via a proton-hopping mechanism.

Enthalpies and free energies of reaction for small neutral and charged beryllium deuterides BeD, BeD 2 , and BeD 3 that have been calculated are reported for a temperature range of 0 K to 1000 K. We discuss probable dissociation channels and possible ways of producing BeD by localizing the relevant transition states and by calculating corresponding rate constants. BeD and BeD + are found to be the most stable ones among the considered compounds. BeD 2 and [Formula: see text] are more likely to decompose into Be 0,+ + D 2 than into BeD 0,+ + D. The metastable BeD 3 and [Formula: see text] predominantly decompose into BeD 0,+ + D 2 . In light of our results on the reaction energetics, we can interpret the pathways for production of BeD via BeD 2 and BeD 3 intermediates observed in molecular dynamics simulations.

We first investigate the feasibility of designing a Fe-oxo complex for the activation of alkane C-H bonds by (a) incorporating an Fe ion into a Zn-based cluster derived from a metal-organic framework (MOF) and (b) creating the Fe-oxo complex via decomposition of N 2 O over a Fe 2+ -substituted Zn-based cluster (Fe-Zn 3 O(pyrazole) 6 ). From the energy profile, it turns out that both steps should be feasible and that the resulting Fe-oxo complex is stable. In the main step, we then investigate the reactivity of this Fe-oxo cluster for the C-H bond cleavage of ethane by calculating the reaction energy profile and analyzing the electronic structure along the relevant steps. Two mechanisms, namely the σ and π pathways on the triplet and quintet potential energy surfaces, were unraveled for this study of catalytic activity. It is shown that the σ pathway on the quintet surface is kinetically and thermodynamically favorable with an energy barrier of 22.5 kcal mol -1 . The π pathway on the quintet and triplet surfaces has activation energies of 26.9 kcal mol -1 and 24.9 kcal mol -1 , respectively. An alternative unusual pathway called the δ mechanism on the triplet surface is also observed with an energy barrier of 12.6 kcal mol -1 . It is, however, thermodynamically at a disadvantage compared to the σ pathway on the quintet surface. Favorable d-d interaction on the Fe center and less steric hindrance from the equatorial ligands at the transition state are the key factors that cause the σ pathway on the quintet surface to have the lowest activation energy. All our calculations are of the cluster type and have been performed at the B3LYP-D3/def2-TZVP level of theory.

The epoxidation of ethylene with N 2 O over the metal-organic framework Fe-BTC (BTC=1,3,5-benzentricarboxylate) is investigated by means of density functional calculations. Two reaction paths for the production of ethylene oxide or acetaldehyde are systematically considered in order to assess the efficiency of Fe-BTC for the selective formation of ethylene oxide. The reaction starts with the decomposition of N 2 O to form an active surface oxygen atom on the Fe site of Fe-BTC, which subsequently reacts with an ethylene molecule to form an ethyleneoxy intermediate. This intermediate can then be selectively transformed either by 1,2-hydride shift into the undesired product acetaldehyde or into the desired product ethylene oxide by way of ring closure of the intermediate. The production of ethylene oxide requires an activation energy of 5.1 kcal mol -1 , which is only about one-third of the activation energy of acetaldehyde formation (14.3 kcal mol -1 ). The predicted reaction rate constants for the formation of ethylene oxide in the relevant temperature range are approximately 2-4 orders of magnitude higher than those for acetaldehyde. Altogether, the results suggest that Fe-BTC is a good candidate catalyst for the epoxidation of ethylene by molecular N 2 O., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mixtures of ethylene glycol with water are a prominent example of media with variable viscosity. Classical molecular dynamics simulations at room temperature were performed for mixtures of ethylene glycol (EG) and water with EG mole fractions of x E = 0.0, 0.1, 0.2, 0.4, 0.6, 0.9, 1.0. The calculated dielectric loss spectra were in qualitative agreement with experiment. We found a slightly overestimated slowdown of the dynamics with increasing EG concentration compared to experimental data. Statistics of the hydrogen bond network and hydrogen bond lifetimes were derived from suitable time correlation functions and also show a slowdown in the dynamics with increasing x E . A similar picture is predicted for the time scales of EG conformer changes and for molecular reorientation. A slight blue shift was obtained for the power spectra of the molecular center of mass motion. The results were used to give a qualitative interpretation of the origin of three different relaxation times that appear in experimental complex dielectric spectra and of their change with x E .

We show, both experimentally and theoretically, that the adsorption of CO2 is sensitive to charge on a capturing model carbonaceous surface. In the experiment we doped superfluid helium droplets with C60 and CO2 and exposed them to ionising free electrons. Both positively and negatively charged C60(CO2)n(+/-) cluster ion distributions are observed using a high-resolution mass spectrometer and they show remarkable and reproducible anomalies in intensities that are strongly dependent on the charge. The highest adsorption capacity is seen with C60(+). Complementary density functional theory calculations and molecular dynamics simulations provided insight into the nature of the interaction of charged C60 with CO2 as well as trends in the packing of C60(+) and C60(-). The quadrupole moment of CO2 itself was found to be decisive in determining the charge dependence of the observed adsorption features. Our findings are expected to be applied for the adsorption of CO2 on charged surfaces in general.

Tungsten-methylidene formation from ethene on either the W(IV) , W(V) , or W(VI) active sites of a W/ZSM-5 zeolite is investigated by using the M06-L functional. The reaction is assumed to proceed in two steps; the first step is the [2+2] cycloaddition between ethene and the W-O active site to form an oxametallacycle intermediate. The intermediate is then decomposed to produce the W-methylidene active site from the metathesis reaction. The overall activation barrier of the reaction on W(VI) (27.3 kcal mol(-1) ) is considerably lower than the ones for W(IV) and W(V) (69.4 and 37.1 kcal mol(-1) , respectively). Moreover, the reaction involving the W(VI) site also stabilizes intermediates and products to a larger extent than the ones on the W(IV) and W(V) sites. As a result, we have demonstrated that the reaction of the W-methylidene metathesis active site is both kinetically and thermodynamically favored to occur on the W(VI) active site of the zeolite., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electron addition to cobalt tricarbonyl nitrosyl (Co(CO 3 NO) and its clusters has been explored in helium nanodroplets. Anions were formed by adding electrons with controlled energies, and reaction products were identified by mass spectrometry. Dissociative electron attachment (DEA) to the Co(CO) 3 NO monomer gave reaction products similar to those reported in earlier gas phase experiments. However, loss of NO was more prevalent than loss of CO, in marked contrast to the gas phase. Since the Co-N bond is significantly stronger than the Co-C bond, this preference for NO loss must be driven by selective reaction dynamics at low temperature. For [Co(CO) 3 NO] N clusters, the DEA chemistry is similar to that of the monomer, but the anion yields as a function of electron energy show large differences, with the relatively sharp resonances of the monomer being replaced by broad profiles peaking at much higher electron energies. A third experiment involved DEA of Co(CO) 3 NO on a C 60 molecule in an attempt to simulate the effect of a surface. Once again, broad ion yield curves are seen, but CO loss now becomes the most probable reaction channel. The implication of these findings for understanding focused electron beam induced deposition of cobalt is described.

A density functional theory study accounting for van der Waals interactions reveals the potential of metal surface vacancies as anchor points for the construction of user-defined 2D patterns of adsorbate molecules via a controlled self-assembly process. Vice versa, energetic criteria indicate the formation of regular adsorbate-induced vacancies after adsorbate self-assembly on clean surfaces. These processes are exemplified by adsorbing C₆₀ fullerene on Al(111), Au(111), and Be(0001) surfaces with and without single, triple, and septuple atom pits. An analysis of vacancy-adatom formation energetics precedes the study of the adsorption processes.

In the interstellar medium (ISM) ion–molecule reactions play a key role in forming complex molecules. Since 2006, after the radioastronomical discovery of the first of by now six interstellar anions, interest has grown in understanding the formation and destruction pathways of negative ions in the ISM. Experiments have focused on reactions and photodetachment of the identified negatively charged ions. Hints were found that the reactions of CnH(–) with H2 may proceed with a low (<10(–13) cm(3) s(–1)), but finite rate [Eichelberger, B.; et al. Astrophys. J. 2007, 667, 1283]. Because of the high abundance of molecular hydrogen in the ISM, a precise knowledge of the reaction rate is needed for a better understanding of the low-temperature chemistry in the ISM. A suitable tool to analyze rare reactions is the 22-pole radiofrequency ion trap. Here, we report on reaction rates for Cn(–) and CnH(–) (n = 2, 4, 6) with buffer gas temperatures of H2 at 12 and 300 K. Our experiments show the absence of these reactions with an upper limit to the rate coefficients between 4 × 10(–16) and 5 × 10(–15) cm(3) s(–1), except for the case of C2(–), which does react with a finite rate with H2 at low temperatures. For the cases of C2H(–) and C4H(–), the experimental results were confirmed with quantum chemical calculations. In addition, the possible influence of a residual reactivity on the abundance of C4H(–) and C6H(–) in the ISM were estimated on the basis of a gas-phase chemical model based on the KIDA database. We found that the simulated ion abundances are already unaffected if reaction rate coefficients with H2 were below 10(–14) cm(3) s(–1).

We performed density functional theory calculations to explore the energetic and geometric aspects of the permeation of H 2 , BeH x , OH x ( x  = 1, 2) and CH y ( y  = 1-4) through the central hexagon of coronene. Coronene serves as a cluster model for extended graphene which can be regarded as the first layer of a graphite (0 0 0 1) surface. We compare the energy barriers encountered by these molecular projectiles with the ones that are obtained for atomic H, Be, C and O. The barriers are substantially lower if projectiles possess free valences that can bind to the carbon entity. Furthermore, for some of the species fragmentation is observed. Implications with respect to plasma-surface interaction are discussed.

In spite of extensive investigations of ethylene adsorbed on graphite, bundles of nanotubes, and crystals of fullerenes, little is known about the existence of commensurate phases; they have escaped detection in almost all previous work. Here we present a combined experimental and theoretical study of ethylene adsorbed on free C 60 and its aggregates. The ion yield of [Formula: see text] measured by mass spectrometry reveals a propensity to form a structurally ordered phase on monomers, dimers and trimers of C 60 in which all sterically accessible hollow sites over carbon rings are occupied. Presumably the enhancement of the corrugation by the curvature of the fullerene surface favors this phase which is akin to a hypothetical 1 × 1 phase on graphite. Experimental data also reveal the number of molecules in groove sites of the C 60 dimer through tetramer. The identity of the sites, adsorption energies and orientations of the adsorbed molecules are determined by molecular dynamics calculations based on quantum chemical potentials, as well as density functional theory. The decrease in orientational order with increasing temperature is also explored in the simulations whereas in the experiment it is impossible to vary the temperature.

Finding novel catalysts for the direct conversion of CO2 to fuels and chemicals is a primary goal in energy and environmental research. In this work, density functional theory (DFT) is used to study possible reaction mechanisms for the conversion of CO2 and C2H6 to propanoic acid over a gold-exchanged MCM-22 zeolite catalyst. The reaction begins with the activation of ethane to produce a gold ethyl hydride intermediate. Hydrogen transfers to the framework oxygen leads then to gold ethyl adsorbed on the Brønsted-acid site. The energy barriers for these steps of ethane activation are 9.3 and 16.3 kcal mol(-1), respectively. Two mechanisms of propanoic acid formation are investigated. In the first one, the insertion of CO2 into the Au-H bond of the first intermediate yields gold carboxyl ethyl as subsequent intermediate. This is then converted to propanoic acid by forming the relevant C-C bond. The activation energy of the rate-determining step of this pathway is 48.2 kcal mol(-1). In the second mechanism, CO2 interacts with gold ethyl adsorbed on the Brønsted-acid site. Propanoic acid is formed via protonation of CO2 by the Brønsted acid and the simultaneous formation of a bond between CO2 and the ethyl group. The activation energy there is 44.2 kcal mol(-1), favoring this second pathway at least at low temperatures. Gold-exchanged MCM-22 zeolite can therefore, at least in principle, be used as the catalyst for producing propanoic acid from CO2 and ethane., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Molecular dynamics simulations of liquid ethylene glycol described by the OPLS-AA force field were performed to gain insight into its hydrogen-bond structure. We use the population correlation function as a statistical measure for the hydrogen-bond lifetime. In an attempt to understand the complicated hydrogen-bonding, we developed new molecular visualization tools within the Vish Visualization shell and used it to visualize the life of each individual hydrogen-bond. With this tool hydrogen-bond formation and breaking as well as clustering and chain formation in hydrogen-bonded liquids can be observed directly. Liquid ethylene glycol at room temperature does not show significant clustering or chain building. The hydrogen-bonds break often due to the rotational and vibrational motions of the molecules leading to an H-bond half-life time of approximately 1.5 ps. However, most of the H-bonds are reformed again so that after 50 ps only 40% of these H-bonds are irreversibly broken due to diffusional motion. This hydrogen-bond half-life time due to diffusional motion is 80.3 ps. The work was preceded by a careful check of various OPLS-based force fields used in the literature. It was found that they lead to quite different angular and H-bond distributions.

We explore solvent dynamics effects in interfacial bond breaking electron transfer in terms of a multimode approach and make an attempt to interpret challenging recent experimental results (the nonmonotonous behavior of the rate constant of electroreduction of S2O8(2-) from mixed water-EG solutions when increasing the EG fraction; see Zagrebin, P.A. et al. J. Phys. Chem. B 2010, 114, 311). The exact expansion of the solvent correlation function (calculated using experimental dielectric spectra) in a series predicts the splitting of solvent coordinate in three independent modes characterized by different relaxation times. This makes it possible to construct a 5D free-energy surface along three solvent coordinates and one intramolecular degree of freedom describing first electron transfer at the reduction of a peroxodisulphate anion. Classical molecular dynamics simulations were performed to study the solvation of a peroxodisulphate anion (S2O8(2-)) in oxidized and reduced states in pure water and ethylene glycol (EG) as well as mixed H2O-EG solutions. The solvent reorganization energy of the first electron-transfer step at the reduction of S2O8(2-) was calculated for several compositions of the mixed solution. This quantity was found to be significantly asymmetric. (The reorganization energies of reduction and oxidation differ from each other.) The averaged reorganization energy slightly increases with increasing the EG content in solution. This finding clearly indicates that for the reaction under study the static solvent effect no longer competes with solvent dynamics. Brownian dynamics simulations were performed to calculate the electron-transfer rate constants as a function of the solvent composition. The results of the simulations explain the experimental data, at least qualitatively.

Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118-281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane-methane and fullerene-methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes., (© 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.)

We report on a previously unknown reaction mechanism involving water in the fragmentation reaction following chemical ionization. This result stems from a study presented here on the humidity-dependent and energy-dependent endoergic fragmentation of allyl methyl sulfide (AMS) upon protonation in a proton transfer reaction-mass spectrometer (PTR-MS). The fragmentation pathways were studied with experimental (PTR-MS) and quantum chemical methods (polarizable continuum model (PCM), microhydration, studied at the MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) level of theory). We report in detail on the energy profiles, reaction mechanisms, and proton affinities (G4MP2 calculations). In the discovered reaction mechanism, water reduces the fragmentation of protonated species in chemical ionization. It does so by direct interaction with the protonated species via covalent binding (C3H5(+)) or via association (AMS·H(+)). This stabilizes intermediate complexes and thus overall increases the activation energy for fragmentation. Water thereby acts as a reusable inhibitor (anticatalyst) in chemical ionization. Moreover, according to the quantum chemical (QC) results, when water is present in abundance it has the opposite effect and enhances fragmentation. The underlying reason is a concentration-dependent change in the reaction principle from active inhibition of fragmentation to solvation, which then enhances fragmentation. This amphoteric behavior of water is found for the fragmentation of C3H5(+) to C3H3(+), and similarly for the fragmentation of AMS·H(+) to C3H5(+). The results support humidity-dependent quantification efforts for PTR-MS and chemical ionization mass spectrometry (CIMS). Moreover, the results should allow for a better understanding of ion-chemistry in the presence of water.

Gas phase dissociative electron attachment (DEA) measurements with methyl-dialanine, C(7)H(14)N(2)O(3), are performed in a crossed electron-molecular beam experiment at high energy resolution (∼120 meV). Anion efficiency yields as a function of the incident electron energy are obtained for the most abundant fragments up to electron energies of ∼15 eV. There is no evidence of molecular anion formation whereas the dehydrogenated closed shell anion (M-H)(-) is one of the most dominant reaction products. Quantum chemical calculations are performed to investigate the electron attachment process and to elucidate site selective bond cleavage in the (M-H)(-) DEA-channel. Previous DEA studies on dialanine have shown that (M-H)(-) formation proceeds through abstraction of a hydrogen atom from the carboxyl and amide groups, contributing to two distinct resonances at 0.81 and 1.17 eV, respectively [D. Gschliesser, V. Vizcaino, M. Probst, P. Scheier and S. Denifl, Chem.-Eur. J., 2012, 18, 4613-4619]. Here we show that by methylation of the carboxyl group, all (calculated) thresholds for H-loss from the different sites in the dialanine molecule are shifted up to a maximum of 1.4 eV. The lowest lying resonance observed experimentally for (M-H)(-) remains operative from the amide group at the electron energy of 2.4 eV due to the methylation. We further study methylation-induced effects on the unimolecular dissociation leading to a variety of negatively charged DEA products.

We report the energy-dependent fragmentation patterns upon protonation of eight sulfides (organosulfur compounds) in Proton Transfer Reaction-Mass Spectrometry (PTR-MS). Studies were carried out, both, experimentally with PTR-MS, and with theoretical quantum-chemical methods. Charge retention usually occurred at the sulfur-containing fragment for short chain sulfides. An exception to this is found in the unsaturated monosulfide allylmethyl sulfide (AMS), which preferentially fragmented to a carbo-cation at m/z 41, C3H5(+). Quantum chemical calculations (DFT with the M062X functional 6-31G(d,p) basis sets) for the fragmentation reaction pathways of AMS indicated that the most stable protonated AMS cation at m/z 89 is a protonated (cyclic) thiirane, and that the fragmentation reaction pathways of AMS in the drift tube are kinetically controlled. The protonated parent ion MH(+) is the predominant product in PTR-MS, except for diethyl disulfide at high collisional energies. The saturated monosulfides R-S-R' (with R

Lithium, sodium and potassium cryolite melts are probed by Raman spectroscopy in a wide range of the melt composition. The experimental data demonstrate a slight red shift of main peaks and a decrease of their half-widths in the row Li(+), Na(+), K(+). Quantum chemical modelling of the systems is performed at the density functional theory level. The ionic environment is found to play a crucial role in the energy of fluoroaluminates. Potential energy surfaces describing the formation/dissociation of certain complex species, as well as model Raman spectra are constructed and compared with those obtained recently for sodium containing cryolite melts (R.R. Nazmutdinov, et al., Spectrochim, Acta A 75 (2010) 1244.). The calculations show that the cation nature affects the geometry of the ionic associates as well as the equilibrium and kinetics of the complexation processes. This enables to interpret both original experimental data and those reported in literature.

We report simulations of the elastic scattering of atomic hydrogen isotopes and helium beams from graphite (0001) surfaces in an energy range of 1-4 eV. To this aim, we numerically solve a time-dependent Schrödinger equation using a split-step Fourier method. The hydrogen- and helium-graphite potentials are derived from density functional theory calculations using a cluster model for the graphite surface. We observe that the elastic interaction of tritium and helium with graphite differs fundamentally. Whereas the wave packets in the helium beam are directed to the centers of the aromatic cycles constituting the hexagonal graphite lattice, they are directed toward the rings in case of the hydrogen beams. These observations emphasize the importance of swift chemical sputtering for the chemical erosion of graphite and provide a fundamental justification of the graphite peeling mechanism observed in molecular dynamics studies. Our investigations imply that wave packet studies, complementary to classical atomistic molecular dynamics simulations open another angle to the microscopic view on the physics underlying the sputtering of graphite exposed to hot plasma.

Bundles of single-walled nanotubes are promising candidates for storage of hydrogen, methane, and other hydrogen-rich molecules, but experiments are hindered by nonuniformity of the tubes. We overcome the problem by investigating methane adsorption on aggregates of fullerenes containing up to six C(60); the systems feature adsorption sites similar to those of nanotube bundles. Four different types of adsorption sites are distinguished, namely, registered sites above the carbon hexagons and pentagons, groove sites between adjacent fullerenes, dimple sites between three adjacent fullerenes, and exterior sites. The nature and adsorption energies of the sites in C(60) aggregates are determined by density functional theory and molecular dynamics (MD) simulations. Excellent agreement between experiment and theory is obtained for the adsorption capacity in these sites.

The solvation structure around the dicyanoaurate(I) anion (Au(CN) 2 - ) in a dilute nitromethane (CH 3 NO 2 ) solution is presented from X-ray diffraction measurements and molecular dynamics simulation (NVT ensemble, 460 nitromethane molecules at room temperature). The simulations are based on a new solute-solvent force-field fitted to a training set of quantum-chemically derived interaction energies. Radial distribution functions from experiment and simulation are in good agreement. The solvation structure has been further elucidated from MD data. Several shells can be identified. We obtain a solvation number of 13-17 nitromethane molecules with a strong preference to be oriented with their methyl groups towards the solute.