arXiv subjects

Piero Ugliengo

Publications and source records attributed to Piero Ugliengo.

At least 19 recordsLinked to original sources

arXiv2026

Astrochemical Inheritance of Terrestrial Planets Water from Local Wet Silicates

The delivery of water to the inner Solar System rocky planets, including Earth, remains debated, as standard models assume that they formed from dry grains, inside the snowline of the protosolar nebula. However, a recent work showed that a not-negligible amount of water formed during the prestellar phase could have been retained by pebbles and planetesimals at the Earth's orbit in enough quantities to reproduce its water content. This study was based based on quantum mechanics (QM) calculations of the binding energy (BE) of water on amorphous ice and on a kinetic approach. Here, we present new QM calculations of the BE of water frozen on the surface of silicate grains, and show that it is on average about twice larger than that on the amorphous ice. The contribution of this first layer of frozen water increases the dust temperature at which frozen water can be retained. This provides a local source of water not only for the Earth, but also for the inner rocky planets. The predictions from our model are in agreement with the available estimates of water content in terrestrial planets. This suggests that water delivery from the outer Solar System may not be required.

astro-ph.EP↗

arXiv2025

FAUST XXIX. OCS line emission: a new method for measuring the luminosity of embedded protostars in binary systems

The luminosity of embedded protostars is commonly measured via observations of the dust continuum spectral energy distribution from millimetre to infrared wavelengths. However, this method cannot be applied to embedded protostars in binary or multiple systems, where their components are usually unresolved over this extended wavelength range. We propose a new method, based on the idea that a molecule formed (mainly) on the grain surfaces only emits lines in the region where it thermally sublimates from the grain mantles, heated by the photons emitted by the embedded source. In this respect, carbonyl sulfide (OCS) is an optimal molecule, because of its low binding energy and rotational lines in the millimetre. We apply the method to the protobinary system NGC1333 IRAS4A, using ALMA high-spatial resolution ($\sim$50 au) observations of the OCS(19-18) line as part of the ALMA Large Program FAUST. We also present new quantum mechanics calculations of the OCS binding energy distribution, essential for the application of the method. We found that the two binary components, A1 and A2, have a comparable luminosity within the error bars, 7.5$\pm$2.5 and 7$\pm$1 L$_\odot$, respectively. We discuss the reliability of the estimated luminosities and the potential of this new method for measuring the luminosity of embedded protostars in binary and multiple systems.

astro-ph.SR↗

arXiv2025

Was Earth's water acquired locally during the earliest phases of the Solar System formation?

The origin of the terrestrial water remains debated, as standard Solar System formation models suggest that Earth formed from dry grains, inside the snowline of the Proto-Solar Nebula (PSN). Here, we revisit this issue through the lens of computational chemistry. While the classically used snowline relies on a single condensation temperature, recent work in quantum chemistry shows that the binding energy of water on icy grains has a gaussian distribution, which implies a gradual sublimation of water rather than a sharp transition. We use the computed distribution of binding energies to estimate the radial distribution of adsorbed ice on the dust grains across the PSN protoplanetary disk. Our model reproduces the full range of estimated water abundances on Earth and matches the hydration trends observed in chondrite groups at their predicted formation distances. Thus, we suggest that a significant fraction of Earth's water may have been acquired locally at early stages of the Solar System formation, without requiring delivery from beyond the classical snowline.

astro-ph.EP↗

arXiv2025

Atomistic insights on prebiotic phosphorylation of methanol from Schreibersite (Fe2NiP) corrosion: ab-initio computational study

The prebiotic history of phosphorus is a matter of debate in the scientific community: its origin, how it landed on Earth, the selective speciation of the phosphate, and its inclusion into the organic matrix are the main unsolved issues. In this regard, Schreibersite ((Fe,Ni)3P), a mineral present in iron meteorites, can play a fundamental role as a carrier of reactive P which, as a result of the weathering processes, produces oxygenated phosphorus compounds, even the phosphate among others. In the present paper, we studied the interaction of methanol (alone and mixed with water) with the Schreibersite surfaces throughout periodic density functional theory calculations at PBE level. The results indicate that Schreibersite promotes the deprotonation of methanol and water both from thermodynamic and kinetic points of view, thus enabling the first step towards corrosion. We have simulated advanced stages of the corrosion process up to the formation of the phosphate and the phosphorylated form of methanol (methyl phosphate), showing that the formation of both products is thermodynamically favoured, as well as its solubilization, which allows other water molecules to proceed with further corrosion of Schreibersite.

physics.chem-ph↗

arXiv2025

The prebiotic pathway from P-bearing iron meteorites to phosphates by DFT modeling

Among the biogenic macroelements, phosphorus is the one bringing the most fascinating and unsolved mysteries for what concern its prebiotic history. It possibly landed on Earth as a metal phosphide (Schreibersite, (Fe,Ni)3P), throughout the Heavy Meteor Bombardment during the Archean Era. Its subsequent corrosion by water led to P-oxygenated compounds, which is the subject of this kinetic computational study, thus complementing our previous thermodynamic characterization. The reaction was studied at periodic DFT level, simulating the water corrosion reaction on the reactive Fe2NiP Schreibersite (001)2 surface. Results show that the timescale of the reaction at 350 K is of few hours.

astro-ph.EP↗

arXiv2024

Unraveling the Interface Chemistry between HCN and Cosmic Silicates by the Interplay of Infrared Spectroscopy and Quantum Chemical Modeling

Understanding the interaction between hydrogen cyanide (HCN) and silicate surfaces is crucial for elucidating the prebiotic processes occurring on interstellar grain cores, as well as in cometary and meteoritic matrices. In this study, we characterized the adsorption features of HCN on crystalline forsterite (Mg2SiO4) surfaces, one of the most abundant cosmic silicates, by combining experimental infrared spectra at low temperatures (100-150 K) with periodic DFT simulations. Results showed the coexistence of both molecular and dissociative HCN adsorption complexes as a function of the considered forsterite crystalline face. Molecular adsorptions dominate on the most stable surfaces, while dissociative adsorptions occur predominantly on surfaces of lower stability, catalyzed by the enhanced Lewis acid-base behavior of surface-exposed Mg2+-O2- ion pairs. On the whole set of adsorption cases, harmonic frequency calculations were carried out and compared with the experimental infrared bands. To disentangle each vibrational mode contributing to the experimental broad bands, we run a best non-linear fit between the predicted set of frequencies and the experimental bands. The outcome of this procedure allowed us to: i) deconvolute the experimental IR spectrum by assigning computed normal modes of vibrations to the main features of each band; ii) reveal which crystal faces are responsible of the largest contribution to the adsorbate vibrational bands, giving information about the morphology of the samples. The present straigthforward procedure is quite general and of broad interest in the fine characterization of the infrared spectra of adsorbates on complex inorganic material surfaces.

cond-mat.mtrl-sci↗

arXiv2024

FAUST XIX. D$_2$CO in the outflow cavities of NGC\,1333 IRAS\,4A: recovering the physical structure of its original prestellar core

Molecular deuteration is a powerful diagnostic tool for probing the physical conditions and chemical processes in astrophysical environments. In this work, we focus on formaldehyde deuteration in the protobinary system NGC\,1333 IRAS\,4A, located in the Perseus molecular cloud. Using high-resolution ($\sim$\,100\,au) ALMA observations, we investigate the [D$_2$CO]/[HDCO] ratio along the cavity walls of the outflows emanating from IRAS\,4A1. Our analysis reveals a consistent decrease in the deuteration ratio (from $\sim$\,60-20\% to $\sim$\,10\%) with increasing distance from the protostar (from $\sim$\,2000\,au to $\sim$\,4000\,au). Given the large measured [D$_2$CO]/[HDCO], both HDCO and D$_2$CO are likely injected by the shocks along the cavity walls into the gas-phase from the dust mantles, formed in the previous prestellar phase. We propose that the observed [D$_2$CO]/[HDCO] decrease is due to the density profile of the prestellar core from which NGC\,1333 IRAS\,4A was born. When considering the chemical processes at the base of formaldehyde deuteration, the IRAS\,4A's prestellar precursor had a predominantly flat density profile within 3000\,au and a decrease of density beyond this radius.

astro-ph.GA↗

arXiv2024

Binding Energies and Vibrational Spectral Features of S$_n$ Species on Amorphous Water-ice Mantles: A Quantum Mechanical Study

In the denser and colder regions of the interstellar medium (ISM), gas-phase sulfur is depleted by 2 or 3 orders of magnitude with respect to its cosmic abundance. Thus, which species are the main carriers of sulfur is an open question. Recent studies have proposed S$_n$ species as potential sulfur reservoirs. Among the various sulfur allotropes, the most stable one is the S$_8$ ring, detected in the asteroid Ryugu and Orgueil meteorite. Shorter species, namely S$_3$ and S$_4$, have been found in the comet 67P/C-G, but their presence in the ISM remains elusive. In this study, we compute the binding energies (BEs) of S$_n$ (n = 1-8) species on an amorphous water-ice surface model and analyze their infrared (IR) and Raman spectral features to provide data for their identification in the ISM. Our computations reveal that these species exhibit lower BEs than previously assumed and that their spectral features experience minimal shifts when adsorbed on water ice, because of the weak and nonspecific S$_n$-ice interactions. Furthermore, these species display very low IR band intensities and, therefore, very accurate instruments operating in the mid-IR range are required for detecting the presence of these species in dense interstellar environments.

astro-ph.GA↗

arXiv2024

Binding energies of ethanol and ethylamine on interstellar water ices: synergy between theory and experiments

Experimental and computational chemistry are two disciplines to conduct research in Astrochemistry, providing essential reference data for both astronomical observations and modeling. These approaches not only mutually support each other, but also serve as complementary tools to overcome their respective limitations. We characterized the binding energies (BEs) of ethanol (CH$_3$CH$_2$OH) and ethylamine (CH$_3$CH$_2$NH$_2$), two interstellar complex organic molecules (iCOMs), onto crystalline and amorphous water ices through density functional theory (DFT) calculations and temperature programmed desorption (TPD) experiments. Experimentally, CH$_3$CH$_2$OH and CH$_3$CH$_2$NH$_2$ behave similarly, in which desorption temperatures are higher on the water ices than on a bare gold surface. Computed cohesive energies of pure ethanol and ethylamine bulk structures allow describing the BEs of the pure species deposited on the gold surface, as extracted from the TPD curve analyses. The BEs of submonolayer coverages of CH$_3$CH$_2$OH and CH$_3$CH$_2$NH$_2$ on the water ices cannot be directly extracted from TPD due to their co-desorption with water, but they are computed through DFT calculations, and found to be greater than the cohesive energy of water. The behaviour of CH$_3$CH$_2$OH and CH$_3$CH$_2$NH$_2$ is different when depositing adsorbate multilayers on the amorphous ice, in that, according to their computed cohesive energies, ethylamine layers present weaker interactions compared to ethanol and water. Finally, from the computed BEs of ethanol, ethylamine and water, we can infer that the snow-lines of these three species in protoplanetary disks will be situated at different distances from the central star. It appears that a fraction of ethanol and ethylamine is already frozen on the grains in the water snow-lines, causing their incorporation in water-rich planetesimals.

physics.chem-ph↗

arXiv2024

Theoretical modelling of the adsorption of neutral and charged sulphur-bearing species on to olivine nanoclusters

Sulphur depletion in the interstellar medium (ISM) is a long-standing issue, as only 1% of its cosmic abundance is detected in dense molecular clouds (MCs), while it does not appear to be depleted in other environments. In addition to gas phase species, MCs also contain interstellar dust grains, which are irregular, micron-sized, solid aggregates of carbonaceous materials and/or silicates. Grains provide a surface where species can meet, accrete, and react. Although freeze-out of sulphur onto dust grains could explain its depletion, only OCS and, tentatively, SO$_2$ were observed on their surfaces. Therefore, it is our aim to investigate the interaction between sulphur-containing species and the exposed mineral core of the grains at a stage prior to when sulphur depletion is observed. Here, the grain core is represented by olivine nanoclusters, one of the most abundant minerals in the ISM, with composition Mg$_4$Si$_2$O$_8$ and Mg$_3$FeSi$_2$O$_8$. We performed a series of quantum mechanical calculations to characterize the adsorption of 9 S-bearing species, both neutral and charged, onto the nanoclusters. Our calculations reveal that the Fe-S interaction is preferred to Mg-S, causing sometimes the chemisorption of the adsorbate. These species are more strongly adsorbed on the bare dust grain silicate cores than on water ice mantles, and hence therefore likely sticking on the surface of grains forming part of the grain core. This demonstrates that the interaction of bare grains with sulphur species in cloud envelopes can determine the S-depletion observed in dense molecular clouds.

astro-ph.GA↗

arXiv2023

Formation of interstellar complex organic molecules on water-rich ices triggered by atomic carbon freezing

The reactivity of interstellar carbon atoms (C) on the water-dominated ices is one of the possible ways to form interstellar complex organic molecules (iCOMs). In this work, we report a quantum chemical study of the coupling reaction of C ($^3$P) with an icy water molecule, alongside possible subsequent reactions with the most abundant closed shell frozen species (NH$_3$, CO, CO$_2$ and H$_2$), atoms (H, N and O), and molecular radicals (OH, NH$_2$ and CH$_3$). We found that C spontaneously reacts with the water molecule, resulting in the formation of $^3$C-OH$_2$, a highly reactive species due to its triplet electronic state. While reactions with the closed-shell species do not show any reactivity, reactions with N and O form CN and CO, respectively, the latter ending up into methanol upon subsequent hydrogenation. The reactions with OH, CH$_3$ and NH$_2$ form methanediol, ethanol and methanimine, respectively, upon subsequent hydrogenation. We also propose an explanation for methane formation, observed in experiments through H additions to C in the presence of ices. The astrochemical implications of this work are: i) atomic C on water ice is locked into $^3$C-OH$_2$, making difficult the reactivity of bare C atoms on the icy surfaces, contrary to what is assumed in astrochemical current models; and ii) the extraordinary reactivity of $^3$C-OH$_2$ provides new routes towards the formation of iCOMs in a non-energetic way, in particular ethanol, mother of other iCOMs once in the gas-phase.

astro-ph.GA↗

arXiv2023

Quantum mechanical modeling of the grain-surface formation of acetaldehyde on H$_2$O:CO dirty ice surfaces

Acetaldehyde (CH$_3$CHO) is one of the most detected interstellar Complex Organic Molecule (iCOM) in the interstellar medium (ISM). These species have a potential biological relevance, as they can be precursors of more complex species from which life could have emerged. The formation of iCOMs in the ISM is a challenge and a matter of debate, whether gas-phase, grain-surface chemistry or both are needed for their synthesis. In the gas-phase, CH$_3$CHO can be efficiently synthesized from ethanol and/or ethyl radical. On the grain-surfaces, radical-radical recombinations were traditionally invoked. However, several pitfalls have been recently identified, such as the presence of energy barriers and competitive side reactions (i.e., H abstractions). Here we investigate a new grain-surface reaction pathway for the formation of acetaldehyde, namely the reaction between CH$_3$ and a CO molecule of a dirty water/CO ice followed by hydrogenation of its product, CH$_3$CO. To this end, we carried out \textit{ab initio} computations of the reaction occurring on an ice composed by 75% water and 25% CO molecules. We found that the CH$_3$ + CO$_{(ice)}$ reaction exhibits barriers difficult to overcome in the ISM, either adopting a Langmuir-Hinshelwood or an Eley-Rideal mechanism. The subsequent hydrogenation step is found to be barrierless, provided that the two reacting species have the correct orientation. Therefore, this pathway seems unlikely to occur in the ISM.

astro-ph.GA↗

arXiv2023

Formation of complex organic molecules on interstellar CO ices? Insights from computational chemistry simulations

Carbon ($^3$P) atom is a reactive species that, according to laboratory experiments and theoretical calculations, condensates with interstellar ice components. This fact is of uttermost importance for the chemistry in the interstellar medium (ISM) because the condensation reaction is barrierless and the subsequent species formed are still reactive given their open-shell character. Carbon condensation on CO-rich ices forms the \ch{C=C=O} ($^3$$Σ$$^-$) species, which can be easily hydrogenated twice to form ketene (H$_2$CCO). Ketene is very reactive in terrestrial conditions, usually found as an intermediate hard to be isolated in chemical synthesis laboratories. These characteristics suggest that ketene can be a good candidate to form interstellar complex organic molecules (iCOMs) via a two-step process, i.e., its activation followed by a radical-radical coupling. In this work, reactions between ketene and atomic H, and the OH and NH$_2$ radicals on a CO-rich ice model have been explored by means of quantum chemical calculations complemented by kinetic calculations to evaluate if they are favourable in the ISM. Results indicate that H addition to ketene (helped by tunneling) to form the acetyl radical (CH$_3$CO) is the most preferred path, as the reactions with OH and NH$_2$ possess activation energies ($\geq$ 9kJ/mol) hard to surmount in the ISM conditions, unless external processes provide energy to the system. Thus, acetaldehyde (CH$_3$CHO) and, probably, ethanol (CH$_3$CH$_2$OH) formation via further hydrogenations are the possible unique operating synthetic routes. Moreover, from the computed relatively large binding energies of OH and NH$_2$ on CO ice, slow diffusion is expected, hampering possible radical-radical couplings with CH$_3$CO. The astrophysical implications of these findings are discussed considering the incoming James Webb Space Telescope observations.

astro-ph.GA↗

arXiv2023

The GRETOBAPE gas-phase reaction network: the importance of being exothermic

The gas-phase reaction networks are the backbone of astrochemical models. However, due to their complexity and non-linear impact on the astrochemical modeling, they can be the first source of error in the simulations if incorrect reactions are present. Over time, following the increasing number of species detected, astrochemists have added new reactions, based on laboratory experiments and quantum mechanics (QM) computations as well as reactions inferred by chemical intuition and similarity principle. However, sometimes no verification of their feasibility in the interstellar conditions, namely their exothermicity, was performed. In this work, we present a new gas-phase reaction network, GRETOBAPE, based on the KIDA2014 network and updated with several reactions, cleaned from endothermic reactions not explicitly recognized as such. To this end, we characterized all the species in the GRETOBAPE network with accurate QM calculations. We found that 5% of the reactions in the original network are endothermic although most of them are reported as barrierless. The reaction network of Si-bearing species is the most impacted by the endothermicity cleaning process. We also produced a cleaned reduced network, GRETOBAPE-red, to be used to simulate astrochemical situations where only C-, O-, N- and S- bearing species with less than 6 atoms are needed. Finally, the new GRETOBAPE network, its reduced version, as well as the database with all the molecular properties are made publicly available. The species properties database can be used in the future to test the feasibility of possibly new reactions.

astro-ph.GA↗

arXiv2022

Where does the energy go during the interstellar NH$_3$ formation on water ice? A computational study

In the coldest (10--20 K) regions of the interstellar medium, the icy surfaces of interstellar grains serve as solid-state supports for chemical reactions. Among their plausible roles, that of third body is advocated, in which the reaction energies of surface reactions dissipate throughout the grain, stabilizing the product. This energy dissipation process is poorly understood at the atomic scale, although it can have a high impact on Astrochemistry. Here, we study, by means of quantum mechanical simulations, the formation of NH3 via successive H-additions to atomic N on water ice surfaces, paying special attention to the third body role. We first characterize the hydrogenation reactions and the possible competitive processes (i.e., H-abstractions), in which the H-additions are more favourable than the H-abstractions. Subsequently, we study the fate of the hydrogenation reaction energies by means of ab initio molecular dynamics simulations. Results show that around 58--90\% of the released energy is quickly absorbed by the ice surface, inducing a temporary increase of the ice temperature. Different energy dissipation mechanisms are distinguished. One mechanism, more general, is based on the coupling of the highly excited vibrational modes of the newly formed species and the libration modes of the icy water molecules. A second mechanism, exclusive during the NH$_3$ formation, is based on the formation of a transient H$_3$O$^+$/NH$_2^-$ ion pair, which significantly accelerates the energy transfer to the surface. Finally, the astrophysical implications of our findings relative to the interstellar synthesis of NH$_3$ and its chemical desorption into the gas are discussed.

astro-ph.GA↗

arXiv2022

Theoretical distribution of the ammonia binding energy at interstellar icy grains: a new computational framework

The binding energies (BE) of molecules on the interstellar grains are crucial in the chemical evolution of the interstellar medium (ISM). Both temperature programmed desorption (TPD) laboratory experiments and quantum chemistry computations have often provided, so far, only single values of the BE for each molecule. This is a severe limitation, as the ices enveloping the grain mantles are structurally amorphous, giving rise to a manifold of possible adsorption sites, each with different BEs. However, the ice amorphous nature prevents the knowledge of structural details, hindering the development of a common accepted atomistic icy model. In this work, we propose a computational framework that closely mimics the formation of the interstellar grain mantle through a water by water accretion. On that grain, an unbiased random (but well reproducible) positioning of the studied molecule is then carried out. Here we present the test case of NH$_3$, an ubiquitous species in the molecular ISM. We provide the BE distribution computed by a hierarchy approach, using the semiempirical xTB-GFN2 as low-level method to describe the whole icy cluster combined with the B97D3 DFT functional as high-level method on the local zone of the NH$_3$ interaction. The final ZPE corrected BE is computed at ONIOM(DLPNO-CCSD(T)//B97D3:xTB-GFN2) level, ensuring the best cost/accuracy ratio. The main peak of the predicted NH$_3$ BE distribution is in agreement with experimental TPD and literature computed data. A second broad peak at very low BE values is also present, never detected before. It may provide the solution to a long-standing puzzle about the presence of gaseous NH$_3$ observed also in cold ISM objects.

astro-ph.GA↗

arXiv2022

Non-Energetic Formation of Ethanol via CCH Reaction with Interstellar H2O Ices. A Computational Chemistry Study

Ethanol (CH$_3$CH$_2$OH) is a relatively common molecule, often found in star forming regions. Recent studies suggest that it could be a parent molecule of several so-called interstellar complex organic molecules (iCOMs). Yet, the formation route of this species remains debated. In the present work, we study the formation of ethanol through the reaction of CCH with one H$_2$O molecule belonging to the ice, as a test case to investigate the viability of chemical reactions based on a "radical + ice component" scheme as an alternative mechanism for the synthesis of iCOMs, beyond the usual radical-radical coupling. This has been done by means of DFT calculations adopting two clusters of 18 and 33 water molecules as ice models. Results indicate that CH$_3$CH$_2$OH can potentially be formed by this proposed reaction mechanism. The reaction of CCH with H$_2$O on the water ice clusters can be barrierless (thanks to the help of boundary icy water molecules acting as proton transfer assistants) leading to the formation of vinyl alcohol precursors (H$_2$CCOH and CHCHOH). Subsequent hydrogenation of vinyl alcohol yielding ethanol is the only step presenting a low activation energy barrier. We finally discuss the astrophysical implications of these findings.

astro-ph.GA↗

arXiv2022

Quantum mechanical simulations of the radical-radical chemistry on icy surfaces

The formation of the interstellar complex organic molecules (iCOMs) is a hot topic in astrochemistry. One of the main paradigms trying to reproduce the observations postulates that iCOMs are formed on the ice mantles covering the interstellar dust grains as a result of radical--radical coupling reactions. We investigate iCOMs formation on the icy surfaces by means of computational quantum mechanical methods. In particular, we study the coupling and direct hydrogen abstraction reactions involving the CH$_3$ + X systems (X = NH$_2$, CH$_3$, HCO, CH$_3$O, CH$_2$OH) and HCO + Y (Y = HCO, CH$_3$O, CH$_2$OH), plus the CH$_2$OH + CH$_2$OH and CH$_3$O + CH$_3$O systems. We computed the activation energy barriers of these reactions as well as the binding energies of all the studied radicals, by means of density functional theory (DFT) calculations on two ice water models, made of 33 and 18 water molecules. Then, we estimated the efficiency of each reaction using the reaction activation, desorption and diffusion energies and derived kinetics with the Eyring equations. We find that radical--radical chemistry on surfaces is not as straightforward as usually assumed. In some cases, direct H abstraction reactions can compete with radical--radical couplings, while in others they may contain large activation energies. Specifically, we found that (i) ethane, methylamine and ethylene glycol are the only possible products of the relevant radical--radical reactions; (ii) glyoxal, methyl formate, glycolaldehyde, formamide, dimethyl ether and ethanol formation is likely in competition with the respective H-abstraction products, and (iii) acetaldehyde and dimethyl peroxide do not seem a likely grain surface products.

astro-ph.GA↗