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.