Ice
• Water makes up more than 60% of ice.
• Ices are believed to cover the surface of a dust core and/or to be physically mixed with dust.

# Papers

• [2022 - ApJS - Quantum Mechanical Simulations of the Radical–Radical Chemistry on Icy Surfaces]
• The radical-radical coupling reactions are not always barrierless on icy surfaces. Each individual reaction should be evaluated individually.
• The switch from D3 to D3(BJ) would lead to different optimized structures of W18 and W33 even if the same functional is used.
• One of the limitation of this paper is that only one reaction site has been considered for the radical-radical reactions on W18 and W33 surfaces. (What is the most realistic way to describe reaction barriers on amorphous surfaces? Would one get a distribution of energy barriers instead of a single value? How to do that?)
• More realistic water cluster models other than W33 are needed in the future and MD will also be helpful to provide more insights into the reactions on icy surfaces.
• [2021 - A&A Germán Molpeceres et al. Binding energies and sticking coefficients of H2 on crystalline and amorphous CO ice]
• ortho-para spin conversion in H2
• Quantities governing the fraction of molecules that return to the gas phase after a collision with an ice surface are sticking coefficients and residence times.
• The sticking coefficient represents the fraction of molecules that remains adsorbed after a collision.
• Residence times quantify the time that a particular adsorbate stays on a surface after adsorption.
• Sampling is based on GFN-FF simulations at 20K and 1000K with a Berendsen thermostat.
• BHLYP-D4 was chosen as the reference method because it offered good description of CO-CO and CO-H2 interactions compared with CCSD(T)-F12/cc-pVTZ-F12
• Rigid scan at different CO-H2 distances is used as the validation of neural network potentials
• [2020 - ApJ - Herbert M. Urbassek et.al.]: Ejection of Glycine Molecules Adsorbed on a Water Ice Surface by Swift-heavy Ion Irradiation (MD-irradiation)
• [2020 - PCCP - Germán Molpeceres and Johannes Kästner]: Adsorption of H2 on amorphous solid water studied with molecular dynamics simulations (QM/MM, GFN2-xTB)
• Sticking coefficients (from 0 to 1, fraction of molecules sticking on surface after a collision) of H2 depends on H2 kinetic energy and the surface temperature, hardly on the incident angle
• Methods for calculating sticking coefficients: analytical model, molecular dynamics (many studies on H, CO, few on H2)
• The surface of amorphous ice is simulated by taking a hemispherical clusters from 18937 water molecules in a periodic cubic cell.
• [2020 - Nat Astro - Alexey Potapov et.al.]: Dust/ice mixing in cold regions and solid-state water in the diffuse interstellar medium
• A substantial fraction of solid water may be mixed with silicate dust grain in the diffuse ISM, protostellar envelopes and protoplanetary disks.
• The desorption temperature of water ice in laboratory is 160 - 180K, depending on the ice thickness and the heating rate.
• The strongest spectral variations can be seen in the 3.1 $\mu m$ (3225.8 cm $^{-1}$) water ice band which provides the cleanest measure of the H2O ice column density in the astrophysical environments.
• Mixing H2O IR spectra at 10K and 150K and comparing with observation is used for determining relative abundance of low-temperature ice and high-temperature ice
• Mixing pure H2O spectra at 10K and 150K: more than 80% ice in protostellar envelopes and protoplanetary disk is low-temperature ice
• Mixing the silicate/ice spectra at 10K and 150K: the low-temperature ice accounts for only about 30-50% of the column mass toward the investigated objects.
• The presence of solid-water in the diffuse medium (where water molecules could be embedded in silicates) is validated by matching 6.2 $\mu m$ water band in the laboratory 200K spectrum and the band in the Spitzer spectrum
• [2016 - PCCP - Martin R. S. McCoustra et.al.]: Peeling the astronomical onion
• [2014 - A&A - Combined quantum chemical and modeling study of CO hydrogenation on water ice]
• I assume that BHLYP (50 % HF) is the same as BHandHLYP
• [2004 - J. Phys. Chem. A - Performance of Density Functionals for Calculating Barrier Heights of Chemical Reactions Relevant to Astrophysics]
• BHandHLYP has 50% HF

## CO2

A way to build CO2 crystal in ase is

## http://rruff.geo.arizona.edu/AMS/CIF_text_files/11286_cif.txt
from ase.spacegroup import crystal
a = 5.624
co2 = crystal(['C', 'O'], [(0, 0, 0), (0.1185, 0.1185, 0.1185)], spacegroup='Pa-3', cellpar=[a, a, a, 90, 90, 90])


## Others

https://www.nature.com/articles/s41467-020-15377-8 vdW interactions are important to water adsorption on surfaces, but have minor effects on the binding geometries

# Talks

## 2020-06 - Sergio Ioppolo - Infrared Resonant Vibrationally Induced Restructuring of Amorphous Solid Water

What we want in experiments are intense lights with tunable frequencies. Pulses are needed as well