Clusteromics IV: The Role of Nitric Acid in Atmospheric Cluster Formation

Abstract

Nitric acid (NA) has previously been shown to affect atmospheric new particle formation; however, its role still remains highly uncertain. Through the employment of state-of-the-art quantum chemical methods, we study the (acid) 1–2 (base) 1–2 and (acid) 3 (base) 2 clusters containing at least one nitric acid (NA) and sulfuric acid (SA) or methanesulfonic acid (MSA) with bases ammonia (A), methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), and ethylenediamine (EDA). The initial cluster configurations are generated using the ABCluster program. PM7 and ωB97X-D/6-31++G(d,p) calculations are used to reduce the number of relevant configurations. The thermochemical parameters are calculated at the ωB97X-D/6-31++G(d,p) level of theory with the quasi-harmonic approximation, and the final single-point energies are calculated with high-level DLPNO–CCSD(T 0 )/aug-cc-pVTZ calculations. The enhancing effect from the presence of nitric acid on cluster formation is studied using the calculated thermochemical data and cluster dynamics simulations. We find that when NA is in excess compared with the other acids, it has a substantial enhancing effect on the cluster formation potential.

Clusteromics V: Organic Enhanced Atmospheric Cluster Formation

“…The general trend of Table is that for smaller clusters the decisive factor is the strength of the acid–base interaction while the effect of steric hindrance becomes more important as the size of the system increases. This is in line with previous findings ,,, along with the observed preference for DMA and EDA at larger cluster sizes and an aversion for TMA.…”

“…The ωB97X-D functional and the 6-31++G(d,p) basis set , were used for obtaining the cluster structures and vibrational frequencies, based on multiple benchmarks. − Vibrational frequencies below 100 cm –1 were treated with Grimme’s quasi-harmonic approximation using the GoodVibes code. The funneling workflow used in this work is similar to the previous clusteromics papers and for a more in-depth description, the reader is referred to these ,,, and our recent review . We applied the following workflow to sample the cluster configurations: ABCluster → PM 7 → sort → DFT → restart → sort → inspection → DLPNO We used ABCluster , to perform initial calculations with the recommended settings from Kubečka et al, which included a population size of 3000 (SN = 3000), a maximum of 200 generations ( g max = 200), and 4 scout bees ( g limit = 4).…”

“…The ACDC , was utilized to simulate the cluster formation potential ( J potential ) using the calculated thermochemical parameters Δ H and Δ S as inputs. The software was downloaded and modified from the ACDC repository − and was employed in line with our previous research. ,,, In the simulations, clusters with a composition of (acid) 3 (base) 2–3 were included and allowed to contribute to the cluster formation potential by leaving the simulation box. However, clusters with the composition of (acid) 2 (base) 3 were excluded as contributors to J potential due to their instability in electrically neutral acid–base clusters. , Default values for coagulation losses typical of the boundary layer (cs_exp = −1.6 and cs_ref = 1 × 10 –3 ) were also used.…”

“…59−61 Vibrational frequencies below 100 cm −1 were treated with Grimme's quasiharmonic approximation 62 using the GoodVibes 63 code. The funneling workflow used in this work is similar to the previous clusteromics papers and for a more in-depth description, the reader is referred to these 34,35,45,46 and our recent review. 64 We applied the following workflow to sample the cluster configurations:…”

“…Nonetheless, formic acid (FA) is a relevant organic acid to investigate due to its hydrogen bonding capability and its high abundance in the atmosphere ranging from 2.50 × 10 9 to 3.75 × 10 11 molecules cm –3 . Similarly to nitric acid, previously studied, this is orders of magnitude higher than the 10 5 to 10 7 molecules cm 3 that has been measured for SA and MSA. − Nadykto and Yu were the first to investigate the interaction between atmospheric nucleation precursors (sulfuric acid, ammonia, water) and common carboxylic acids (formic and acetic acid) using quantum chemical methods. From their calculations, they suggested that FA had a stabilizing effect similar to that of ammonia (A), indicating that these organic acids may effectively stabilize small SA–water clusters.…”