Bulk Properties#


Intro paragraph


  • Summary




Fig. 16 Source#


ie purely amorphous, no crystaline nuclei


Hydrogen bonding#

[Parmentier et al., 2015]

“H-atom dynamics in several forms of ASW, inelastic neutron scattering, mean kinetic energies increase with increasing density (weaker H-bonds) vibrational potential energy surfaces get steeper, change in O-H stretching component with density stronger than suggested by e.g. Raman spectroscopy”


  • [Manca et al., 2002]: Porosity & SSA of ASW & crystalline ice, N2, CH4 and Ar adsorption, adsorption isotherm volumetry & infrared spectroscopy, non-microporous ice can have large SSA

What pores ?#


Insert Sabrina article on pore shape

Insert sabrina article

[Maté et al., 2012]

Evolution with temperature#


  • [Isokoski et al., 2014]: Compaction of ice (H2O, CH3OH, CO2, mixed H2O:CO2 = 2:1) upon heating, astronomically relevant T-range, Laser interference & FTIR, for ASW the full loss of dangling OH bonds is not a proof for full compaction, for other ices thermal segregation benefits from higher degree of porosity.

  • [Bossa et al., 2012]: ASW pore collapse, 20 -120 K, thickness (optical interference) & porosity/phase (FTIR) measurements, porous ASW: thickness decreases by (12 ± 1) % between 20 and 120 K, less porous ASW: smaller thickness decrease, crystalline ice: negligible thickness decrease.


[Cazaux et al., 2015]


Trapping of molecules#


Big topic !!

  • Find intellegent method of classification … Per molecule studied ?


Link with ethane deposition type

  • sequential

  • co-deposition

  • [Gálvez et al., 2008]: SSA of ASW: Spectroscopy on CO2 ice (trapped in ASW pores), deposition at 95 K (simultaneously or sequentially), CO2 infrared bands shift & split in both cases (interaction with water molecules), larger amount of CO2 trapped in ASW in co-deposition, in sequential deposition most CO2 trapped in macropores of ASW, phase transition at 140 K -> CO2 molecules relocate -> similar bulk structure to co-deposited samples

  • [Malyk et al., 2007]: Trapping and release of 13CO2 by porous ASW (13CO2 on top of/below/codeposited with ASW), TPD & FTIR, some 13CO2 becomes trapped when annealing ASW (amount depends on deposition method), two stage release of trapped 13CO2: 1. majority escapes at ASW-to-cubic transition (165 K), 2. rest desorbs together with cubic ice (185 K) -> must be trapped in cavities that do not open during crystallisation.

  • [Raut et al., 2007]: Porosity of ASW via quartz crystal microgravimetry, UV-visible interferometry, and infrared reflectance spectrometry in tandem with methane adsorption: microporosity for all deposition methods, but collimated depositions show additional mesoporosity (up to 140 K (crystallization)), higher binding energy for collimated deposition, methane on dangling OH bonds -> no multilayer condensation inside micropores (methane coating the walls instead of filling the pore volume).


[Bu et al., 2016]

Specific Surface Area#

  • SSA (Definition).


Molecular diffusion occurs as a result of thermal motion of the molecules.

[Smith et al., 2000]

Models of diffusion#

[Ghesquière et al., 2015]


[Speedy et al., 1996]: Free energy difference (ΔiaG (150 K) = 1100 J/mol) & residual entropy difference (ΔiaS (0) = 0.7 J/(K mol)) for ASW & crystalline ice, from evaporation rates, ΔiaS (0) allows connection of ASW with normal liquid H2O via reversible thermodynamic path (1 atm).

Thermal desorption formula (test)

\[ k_{td,i} \simeq \nu _{i} e ^{-\frac{E_{b,i}}{k_{B} T_{S}}} \]


[Bu et al., 2015]: Surface voltages (Vs) of ASW (vapour deposited below 110 K), Kelvin probe measurements, Vs increases with film thickness & decreases with deposition T & angle, decreases by ≈ 80 % when annealed 30 K above deposition T, -> polarization in ASW is governed by incompletely coordinated water molecules, dangling with unbalanced dipoles at internal surface of pores


Hence the importanceof characterising the HB network in ASW

Structural relaxation#

[Shephard et al., 2013]: LDA (prepared from HDA or vapour deposited) annealing, Raman & FTIR spectroscopy, structural relaxation -> increase of local and long-range order (starting before crystallisation and not finished at onset of crystallisation) -> contradicting findings on glass transition.

2 distinct structural state ?#

Neutron diffraction: [Winkel et al., 2009]: Neutron diffraction on low density amorphous ice (produce from high density ASW by isobaric warming or very high density ASW by isothermal compression), -> two different forms of LDA (different compression behaviour & structures (atomistic modelling -> competition between short & intermediate order & disorder)).


To classify

  • [Manca et al., 2004]: Adsorption isotherm volumetry & FTIR spectroscopy, ASW characterisation (porosity, SSA, crystallisation), annealing induced modifications, number of surface sites decreases before crystallisation, non-microporous ice can have large specific surface area.


Good article, to read.

Structure factor#


To define (ROO)

[Barker et al., 2000] oxygen-oxygen structure factor SOO(Q) peak of liquid water shows unusual doublet structure (shifting with pressure), limits correspond to peak positions of low/high density ASW -> polyamorphism of H2O, position determined by nearest-neighbour separation of voids in spatial distribution of oxygen atoms

Variation w/ experimental conditions#

Deposition angle#

  • [Dohnálek et al., 2003]: ASW characterisation (laser optical interferometry): film thickness & density of ASW films (vapour deposited @ 22 K, collimated molecular beam, angle varied between normal & oblique incidence), normal incidence films presumed to be compact (0.94 g/cm3), glancing incidence ρ = 0.16 g/cm3 (> 80 % porosity), in agreement with ballistic deposition simulations.

[Stevenson et al., 1999]


[Maté et al., 2003]: ASW & crystalline H2O ice (vapour deposited), < 100 nm – 5 μm thickness, FT-RAIRS, Al & Au substrates (similar results for both), optical effects (surface suppression/vibrational mode enhancement) vary with thickness, spectral simulations (Fresnel model)

Phase transition between polyamorphs#

Occur in a very narrow temperature-pressure interval (more info) and is characterized by sudden, step-like changes in properties such as:

  • Density

  • Coordination number

  • Isothermal compressibility

Furthermore, tha transitions can be reversed with hysteresis, (typical from first order transition)


define the different type of transitions.