Binding Energy Evaluation Platform: A Database of Quantum Chemical Binding Energy Distributions for the Astrochemical Community

Abstract

The quality of astrochemical models is highly dependent on reliable binding energy (BE) values that consider the morphological and energetic variety of binding sites on the surface of ice-grain mantles. Here, we present the Binding Energy Evaluation Platform (BEEP) and database that, using quantum chemical methods, produces full BE distributions of molecules bound to an amorphous solid water (ASW) surface model. BEEP is highly automatized and allows one to sample binding sites on a set of water clusters and to compute accurate BEs. Using our protocol, we computed 21 BE distributions of interstellar molecules and radicals on an amorphized set of 15–18 water clusters of 22 molecules each. The distributions contain between 225 and 250 unique binding sites. We apply a Gaussian fit and report the mean and standard deviation for each distribution. We compare with existing experimental results and find that the low- and high-coverage experimental BEs coincide well with the high-BE tail and mean value of our distributions, respectively. Previously reported single BE theoretical values are broadly in line with ours, even though in some cases significant differences can be appreciated. We show how the use of different BE values impacts a typical problem in astrophysics, such as the computation of snow lines in protoplanetary disks. BEEP will be publicly released so that the database can be expanded to other molecules or ice models in a community effort.

Simulation of CH$_3$OH ice UV photolysis under laboratory conditions

“…Appendix C contain the list of newly added surface photolysis and Appendix D shows the bimolecular surface reactions and binding energies used in this paper cross-checked against Wakelam et al (2017). We highlight that we assume the binding energy as a single value, and not as a distribution as discussed by Shimonishi et al (2018), Grassi et al (2020), Bovolenta et al (2022), Villadsen et al (2022), andMinissale et al (2022). In addition to the methanol formation and destruction pathways included in these lists, we have added the methanol ice photodissociation routes (see Table 1).…”

Reaction dynamics on amorphous solid water surfaces using interatomic machine learned potentials. Microscopic energy partition revealed from the P + H -> PH reaction

“…While we start our sequential simulations with P atoms in VW and WB binding sites along with MB and HB, we find that PH populates only HB and MB sites at the end. This is an essential conclusion of our work, pointing to the fact that nascent molecules arising from exothermic radical-radical recombination are unlikely to be found in the weak binding sites on a pristine surface and affecting the (effective) distributions of binding energies recently reported in the literature for low-temperature studies (Ferrero et al 2020;Duflot et al 2021;Bovolenta et al 2022). The population of HB and MB sites comes as a result of non-thermal diffusion of the nascent PH molecule that uses part of the reaction energy to freely roam the surface until landing on an HB or MB site.…”

“…Even though the changes portrayed in Table 6, Modified Values A, are minimal and fall within the variability for binding energies as presented by various methods for other adsorbates (Das et al 2018;Ferrero et al 2020;Bovolenta et al 2022), we ob-serve a significant increase in the abundance of gas-phase PH 3 by four orders of magnitude. The changes for the Modified Values B are even more drastic because they disregard average and deep binding sites (MB and HB), and we equally observe variations of 5 orders of magnitude in the P-bearing abundances with respect to the values using the original average BE, approaching the values predicted by a constant probability of chemical desorption.…”

Simulation of CH3OH ice UV photolysis under laboratory conditions

“…Appendix C contains the list of newly added surface photolysis, and Appendix D shows the bimolecular surface reactions and binding energies used in this paper, cross-checked against Wakelam et al (2017). We highlight that we assumed the binding energy as a single value, and not as a distribution as discussed by Shimonishi et al (2018), Grassi et al (2020), Bovolenta et al (2022), Villadsen et al (2022), andMinissale et al (2022). In addition to the methanol formation and destruction pathways included in these lists, we added the methanol ice photodissociation routes (see Table 1).…”