 Thank you very much. Thank you very much. Thank you. So now is the turn of Ali Hassan Ali from ICDB The title of the talk is understanding fluctuations in water in a molecular perspective so Ali, please. Yeah, I'm just waiting to okay. Let me I Screen Okay, do you see my screen? Yes. Okay Let me Thank you Uriel for The kind introduction and where's my screen there we go. So I'm sorry I changed the title of my talk last minute But the message is going to be the same and basically what I want to tell you about today is on the many faces of water basically on the computer and So I want to start with a bit of popular culture Which is if you're looking for inspiration on the many faces of water This is really nice TV series that ended last year unfortunately called the game of thrones and in the game of thrones is this guy called the white knight Who's made up of ice? And it's a it's a really interesting series, but if you're looking for it Sorry, what what is that our white knight? Is it the king of a knight or a knight king? No white knight king. Thanks No, it is it's very important and So if you're looking for inspiration on on different phases of water, that's a good place to start So the question I want to ask today is basically is water a silent spectator in many of the the processes that we are interested in as chemists physicists or biologists or even as engineers and What I've been interested in for for a while now is trying to understand Molecular fluctuations in liquid water So I know that we have a rather diverse audience here and so I just wanted to give you a bit of context so If you are interested in any type of chemical reaction in water Or any chemical reaction in sort of solution chemistry all those chemical reactions happen in a solvent environment and if you open up any textbook in basically general chemistry or physical chemistry The the role of the solvent in chemical reactions in physical processes is is sort of a rather mysterious object That's sort of put under the rug On the other side if you if you come from the soft matter Community you're obviously well aware that you know processes like protein folding The development of lipid bilayers you've some of the things you've heard in today's talks All these processes happen in the water and so what I'm interested in doing along with my collaborators is combining Both atomistic simulations as well as smart data mining to learn new physics and chemistry essentially And so What I want to do in in my talk today is not getting to any specific results Or not too many specifically just to give you an overview and a context of Maybe some of the things that you'll hear about in the talks to follow So, you know water is a is an extremely interesting and weird and also a very controversial Liquid in the literature So, you know, you've all sort of seen these types of plots most liquids Well, you know when you increase temperature the density decreases Liquid water is this anomaly which is that is a density maximum at 40 degrees Celsius You can also look at other thermodynamic properties like the compressibility and the heat capacity and when you look at the compressibility of water It has this interesting minimum at 319 Kelvin and then as you undergo cooling the compressibility increases And so a lot of these anomalies in water have been attributed to it's the hydrogen bond network So, you know liquid water is is on average a tetrahedral Structure so it accepts and donates two hydrogen bonds on average and they've been numerous debates in the literature on What is really the origin of these anomalies and also more importantly, what is the molecular structure? Of what and I'm just sort of giving showing you here Some of these papers that have been published Both experimental and theoretical work. So this is an interesting review Couple of years ago Discussing that liquid water and room temperature Exists as two co-existing liquids There's this very recent very interesting work by Pablo de Benedetti and Francesco Schortino and published in science just last month Where they did a very long molecular dynamic simulation So microseconds and microseconds of several water models and where they claim or they find from their simulations a second critical point In in now a realistic water model And these are two at the bottom here are the interesting Titles This is a paper published last year by Bill Goddard's group Claiming that liquid water is a dynamic polydispersed branched polymer Which was very quickly Rebuddled by Francesco Presani and Teresa had Gordon Saying water is not a dynamically poorly dispersed branched polymer. So that you know the You'd think that water being one of these the most ubiquitous liquid been studied for Centuries essentially that we would have figured all of it out But it continues to pose a lot of interesting puzzles and I want to If there's one thing I want you to take away from my presentation is is is basically in this slide and and that is the role and importance of non-local chemistry and So if you're if you're a physicist You might be more inclined to thinking about the role of collective fluctuations. Okay, and So this is related to a problem where where I actually got interested in this and that is the ionization of water So in in textbook chemistry They'll you will maybe teach this or you'll write the ionization of water as this chemical reaction here And so basically it's two H2O get gives you the hydronium ion and the hydroxide ion and Chemistry textbooks are full of these types of Chemical reactions Where the solvent bath is sort of ignored or not thought to play an important role in the process Or it's it's assumed that it's it's important, but it's not really understood how and why so I want to play this movie for you which is a a movie of the time-reversed process of the Ionization of water, which is the recombination and I'll start to play it now and what you're going to see here is so this is on the left side is the positive charge Which is the hydronium ion so this guy here and then on the right side is the negative charge Which is the hydroxide and I'm only showing Those ions with some water molecules sandwiched in between and the rest of the bath is blurred out Which are going to see something very interesting happen So you just saw that the single proton tried to jump across a hydrogen bond and Then there's some fluctuations in the liquid and eventually There's a Collective breathing mode in the liquid along this sort of wire that leads to these three protons hopping along the wire and Leading to neutral water And so this was really the the starting point for me in thinking about the types of Collective fluctuations in water and why this is interesting and challenges that challenging is that you've got three different components that need to be Integrated into each other one is the role of density fluctuations The other thing is that water is a directed network, so it has some interesting topological properties so you have to understand the coupling of both topology and density and Finally a very important aspect that plays into role, especially in processes like this is the role of charge Transfer, okay And so this is an example of a of a really basic chemical reaction in water Which determines the pH of water so the number of the concentration of protons in solution But who's underlying thermodynamics and kinetics and mechanisms is still actually not completely understood So I want to give you just one example of Recent problem that we've been interested in and that is related to density fluctuations and it's possible implications Sorry Ali, can I ask a question from you? Yeah What is the underlying interactions Concluded in the simulation that you show the film of it What is the what is the underlying principles in the simulation? So basically this this actually relates to something that Ali Najee had in one of the slides which is essentially, this is the distance where At the Buram length Where the where the electrostatic energy gets much larger than thermal energy? And so when you get to this to this Critical distance you've got, you know the very strong charge charge interactions that drive these proton transfer Processes, so it is not any kind of quantum interactions included in this in this simulation You mean practically, okay, so yes, these are ab initio DFT molecular dynamics All right. I see. Thank you. Thanks Okay, so I want to say a bit about density fluctuations and possibly With some crazy implications on the origin of life And so what I've been interested in for a while is inserting Hydrophobic solutes in water and so one way to think about hydrophobic salvation is if you have a box of waters Essentially, if you want to create or put a hydrophobic solute in it, you have to wait for Sometime before an empty space Gets available. Okay, so you sit yourself in your water network You study the density fluctuations and you wait until, you know, you create an an empty space Where you can then insert a hydrophobic solute in so they've been Decades and decades of work done on this but mostly people focusing on The salvation of spherical cavities Okay, so you can ask questions like what is the thermodynamics associated with the creation of spherical cavities? of different sizes and this is related to the free energy of Putting a hydrophobic solute inside and so We started to to revisit this and I'll just essentially tell you the result Which is we've been using a lot of classical MD along with a technique a technique known as a veranoid void tessellation and What I'm showing you here are distributions of the normalized volumes of voids empty spaces found in liquid water and in liquid methane and What you find is that there's a Both liquids are dominated by Objects that look like like spherical cavities, but then you have this long tail of Cavities here that look like all these exotic Shapes that you find here and if you stare hard enough you might find a guy shooting a basketball net and Also a small dinosaur But the the take-home message here is that then the spontaneous fluctuations in These two liquids water and methane lead to these transient dry spots that are quite delocalized and with rather exotic dendritic shapes and If you start staring at these long enough You might begin to think and ask well Some of these look like possibly small polymers and so Could there be some interesting Relationship between the thermodynamics of the creation of these shapes and the thermodynamics of solvating small hydrophobic polymers And and the answer is yes, and so I don't have time to to go into the details. This is a work done by a brilliant postdoc in our group who left Nargis Ansari and so what we discovered by doing Simulations of lots of different small polymers. So for me a polymer is you know an object that looks like this So it has six to ten membered chains and what you can find is that there are shapes that Naturally occur in the liquid through density fluctuations Without the polymer that are consistent with the shapes that the polymer takes and You can also do the thermodynamics. You can ask what is the free energy to solvate a Polymer like the one on the on the left and the one on the right Versus the thermodynamics of the creation of these empty spaces and the two are are essentially consistent And so what this is sort of suggesting is that you know that they are these spontaneous fluctuations of the liquid This is true for both actually liquid water and liquid methane that Sorry, we have a question from now on Yes, hi Ali. So yes questions like that. There are zillions of these shapes Are always you can find some particular it could be a shape of my face or anything else because of the fluctuation so how can means Say about like the you can find Mostly or maybe like cat like or dinosaur like or what? Yeah right, right so So basically You can because we have you have statistics, right? So, you know in an ensemble you have a million voids Okay, then you can ask out of those a million voids. How many of them are In just for the sake of argument branch shaped like the one I'm showing you Okay, so then then you then you know what the free energy is to create a branch shape void and Then you you can compare that to the free energy That you get from like thermodynamic integration of Solvating a branch shape like how you get filter for these branch shapes means is there some criteria like some particular shape Leap for long or I don't know means have three energies Much lower compared to other that you filter them out and then you have to study them later Or what what is the criteria to filter out the? so so in the case of For example in the case of the the the branch shaped We have a we have a way to to ask what is the or to quantify? What is the overlap in the? The ensemble of the branch shape polymer when the polymer is there to When the polymer is not there So we have we have a way to match it Basically, yeah, okay. Thank you Ali. Thanks So So it's okay without going into details what one can then do is and sort of ask how does this change as a function of the phase diagram of water and I don't have time to get into this but what's interesting is if you undergo super cooling Whether a lot of these interesting anomalies you get the clustering of these large voids informing large connected regions of empty space Okay Okay, so in the last couple of minutes of my talk I want to just Go ahead Riza Okay, and just I'm wondering that's if the if some kind of the polymers can fill this Voids maybe if you look at the solubility of the different Polymers we can we should find something very a Peak when the size of the polymers or shape of the polymer are the size of the boys that you have here Fantastic point. Yes. That's a great question So we we only measured the solubility for these class of polymers Six to ten my my guess is that Anything above 14 Would have a big drop in the solubility because It becomes much rarer and rarer to find those things through spontaneous fluctuations I'm just wondering if in the experiments people have seen such kind of the The point the point is the Well, you would have to yes So one would have to design a polymer like the ones that I have like wire versus branch for example And try to see as a function of increasing the size In a wire versus branch. Do you see a peak in the solubility? Yeah, that's an interesting question. Yes That's a I don't think anyone's done it. No, but yeah Okay, so In the last couple of minutes that I have I just want to let's say get some perspectives on Where I think the real interesting stuff is happening in the field of it's a physical chemistry of water There's a lot of interesting problems in interfaces So whether you're looking at a glass of water or you're sitting on the sand Looking at silica water interfaces or you're dealing with proteins all of these substances involved some boundary between one surface and another and The question the basic question is the following How does the structure and dynamics and electronic properties of water change? near these interfaces Okay, and so there's lots and lots of experiments and also simulations Showing and suggesting and again full of controversies on the extent of these perturbations that changes And so I just want to motivate one of the examples. You'll hear about this more from Ricardo Either tomorrow and Friday and that's related to soap bubbles so we've been a part of a project here that's related to artificial photosynthesis which sort of Has this idea that one can use soap bubbles To emulate what a leaf does and so a leaf Takes light and converts that into chemical energy, right? And so the idea is can one synthesize artificially a Membrane or a series of membranes and proteins like you'd have in a leaf in a soap bubble morphology And so I will not get into the details since Ricardo will show some of these results, but there's some very interesting Questions and this is one of my last slides that that come up from these types of synergies So this is a snapshot of the simulation of this water with a surfactant so like the one that Edgar was talking about and so some of the questions that One can ask in what experimentalists are interested in are for example, what is the thickness of the interface? How much water penetrates into the surfactant? What is the role of orientation of electronic polarization at the interface? To what extent and by how much does water slow down in these regions? Can one measure a local viscosity for example That can Be used in you know continuum type models like the ones that Ali Najee was talking about as well as Ali Rajapur And finally if you've got solutes like water or gases that are moving through the interface How do they diffuse through and are they traps that affect the diffusion? So this is a problem that we're Interdisciplinary a joint collaboration with the the people That I've listed in the bottom and I'd be interested to hear some of your thoughts on addressing these types of questions I'll end with this slide here. So Going back to this where I started So I'm a firm believer in the use of atomistic simulations I've sort of been Slightly yes, we're a little bit over time Fine, fine. I stop I stop I stop I stop So unfortunately, we don't have time for more questions in fact Is a will kind of will lose the Loose at the time of the break because the break was supposed to be until five and it's 504 so I Succeeds to continue with the next talk Just to respect the program is scheduled because Everyone's just just a five minute breaks. I think we anyway If everyone will be able to do that, maybe they have other commitments or I don't know if everyone is okay We can take five minutes, but if someone is not okay, just say it and we can continue