Here is the current version of the slides.
There is some interesting local background history I will briefly mention in the talk. One of the first people to document correlations between different properties (e.g. bond lengths and vibrational frequencies) of diverse classes of H-bond complexes was George Pimentel.
Many correlations were summarised in a classic book, "The Hydrogen Bond" published in 1960.
He also promoted the idea of a 4-electron, 3 orbital bond which has similarities to the diabatic state picture I am promoting.
There is even a lecture theatre on campus named after him!
Caveat: I'm a novice in this subject, but it raised a question for me if and how the following could be related to hydrogen bonding.
ReplyDeleteI recently heard a very nice talk by Alexey Sokolov who had convincing evidence for quantum effects (zero point energy) in supercooled water being significant at relatively high temperatures (150 K or so).
As that was my first introduction to this subject, I can't say whether this is all old news, but I liked the simplicity of the dielectric relaxation experiments providing the data for these conclusions. (They also did inelastic neutron scattering.)
This talk was based mostly on PRE 91 022312 (and there was a PNAS and PRL before this work, refs 46 and 90 in the PRE).
Thanks for bringing this work to my attention. It is certainly relevant. I looked at the papers. The PNAS is the most helpful as it clearly shows H/D isotope effects.
DeleteI tend to avoid the glass transition in water as the data and interpretation is usually quite controversial.
I don't find the fact that there are significant isotope effects (and thus quantum effects) for supercooled water at all surprising since they are also present for regular liquid water and ice.
I actually disagree with a number of statements in the PNAS paper. This probably justifies a separate blog post. I think the framework I am advocating can be more definitive about some of the issues. For example, I think the key variable is not M=mass of the molecule, but the mass of hydrogen and the (H-bond) donor-acceptor distance.
In the next week I will see a couple of experts on this water glass transition and so look forward to discussing it with them.
My understanding of the seminar was that indeed it's the mass of the proton, not the molecule, that mattered.
ReplyDeleteNH3 and HF also came up in some discussion (though I suspect not a lot of people want to experiment with HF...).