 Hisham, can you hear me now? Okay, great. So you can hear me? Yes, we can hear you. Very good news. Yeah, well, I can imagine. So we were looking for you. Thank you. What about now? Can you see my screen? We can see you, yes. Not your screen, but I can see your video actually, your face. Okay, let me try again. What about now? Perfect. Good at last. Yes. Nice to see you again. Okay, so welcome. Welcome, Prof. So this is our today's morning. Last session. So after this session, we will have the interaction session. So you have 20 minutes talk and then five minutes interaction. Thank you very much indeed. I'm sorry for this inconvenient situation. But things are fine. My name is Hisham Abdullah. I come from Sudan. And I work as professor of physics at Sultan Kabul University in Oman. And this work that I'm showing you here actually is done in collaboration with colleagues at Khartoum University and other places. So this is why I have to mention that in the beginning. Okay, as you can see, I'm going to talk about iron oxides, both binary and ternary, but I'm going to choose all literary oxides. This means that there are two cations and one anion. So as you can see, they are having oxygen, low spec structure. Where the cations occupy interest sizes between the, between the oxygen anion, this can be octahedral tetrahedral sites and this can be, for example, if I'm talking about iron in particular can be iron two and three and four and even iron five. So all these situations that can be there. And of course, if there's another iron or a curtain also can occupy another site. Okay, so the size now will be occupied by both cations. The physical and chemical properties of this material as any other material actually depends on the structure. And this properties can be modified by choosing certain top and ions. So we can either do by choosing a particular iron or you can alternatively make the size is small to the nanoscale or you can combine both actually what we do in our group we try to combine both ionic doping and also reduction of the size to the nanoscale so that we can modify the properties of this material so that we can get interesting properties for new applications. I'm going to start with two actually materials, and my talk will be all these two materials to be spinel pervocyte. The first one spinel actually is magnetite and the pervocyte is is European iron oxide. I'm not going to talk about it as I mentioned in my, in my structure. As I said to you the change of the properties actually can be done by either reduction of the size, which mean that we're going to have distorted or this order actually surface structure which actually leads to interesting properties and also if you don't discuss and we're going to create some sort of defective structure that has to be explored in order to understand why the changes took place in the properties. What we do actually, as you hear from my title, we do actually use the experimental techniques to investigate the structure and the material properties and so on, and then try to understand how that happens because sometimes you know when you use experimental techniques then you just fit data, so sometimes you need to go deep and do some sort of computational and theoretical work and here, as you can see I'm using both atomistic simulation and DFT modeling and of course this is done with my colleagues and my students. These are the new articles that we have published recently, so if you're interested then you can see that, but it's clearly from this list that we work with iron oxide and we dope them. And I'm going to choose only magnetite as an example for spinel materials and at the nanoscale this material has a lot of applications ranging from direct delivery to contrast agents in magnetic resonance imaging and so on. So it's very important and this material of course is very, has been studied intensively but still it's very interesting for people to investigate the properties of the nanoscale in particular. And this is a structure actually of spinel, I'm sure a lot of people here know this structure, you have a base center cubic structure of oxygen where as I said to you, you have interest sizes, which are either tetrahedral where the cation is coordinated with four oxygens or octahedral where it's coordinated with six oxygens and in this particular case, the structure is not actually normal spinel, it's invested spinel, which means that the divalent ion rather than going to the tetrahedral site as the case in normal spinels, it goes to octahedral site, we call them B and then the cations, the trivalent cations are evenly distributed between the octahedral site and the tetrahedral site. Well, let me go back to the nanoscale problem. If you prefer this particle as nanoparticles then of course the surface area of these nanoparticles will be exposed to air and then there's a chance of oxidation of ion two to ion three, which means that the magnetite will transform to magmaite, which is a big problem actually because magmaite has lower magnetic properties which will not of course help the material to be used as for example contrast agent in MRI. Well, magmaite itself, which has the same spinel structure, if it is heated it will convert to hematite. And the other thing which I want to mention in terms of the magnetic properties, this material as I said has two magnetic sublattices octahedral where you have ion two and ion three, as you can see here, ion three has fd5 electrons and that's 60 and then there's some sort of electron hopping between the ions in what is octahedral site and then we have the tetrahedral site where you have the ion three. And these two sublattices are anti ferromagnetically coupled leading to a ferromagnetic material whose magnetization is given by what by the difference in the magnetization of each one of these sublattices. So it's clearly that if you introduce a cation then the cation of course can either decrease or what or increase the magnetization depending on where it goes. So one of the things that we try to do is to understand the position occupied by the dopant cations and particularly in this project actually we were using the divalent cations like this ones are shown here zinc or tin or manganese to approach is different from the approach that has been done in the past because people in the past either used to replace or substitute ion two by what by divalent ion or replace ion three by what by either divalent sorry tetravalent or trivalent ions. So here our approach is different and what you want to do actually want to replace ion three by what by ion two. So as I mean that we have to have three ion two for for every 33 divalent ions for every two ferric ions and of course depending on where the divalent cation goes then of course the properties can change. So I'm going to talk about manganese dop magnetite and clearly here x is equal to two-third of what of of why because we need charge balance, and this is how charge balance is what is achieved. Okay, I'm going to talk about the experiment that we have done and also I'm going to talk about about modeling that we have done to study the structure and the magnetic properties. So these materials I'm not going to talk about how they were in society, but they were in society as clear from here by by the precipitation technique, and clearly this XRD showed that depending on the. It doesn't matter when you do eventually are getting the same structure. So we are sure now from this XRD that you have single phase compounds where the manganese does not change structure. So I'm happy that the lattice parameter has shown us that manganese is incorporating the structure because as you can see it increases monotonymatically and this is a key and results shows that you have, as you can see, we have nanoparticles whose every size is just around 15 nanometer. And after that, of course, we did the structure characterization using Raman's spectroscopy, and I just want you to look at the sample which has X equals zero, which is a end up sample. Clearly the spectrum is different from from that of the of the magnetite which is clearly in the other samples. Here we have peaks that are for hematite, you don't know where hematite comes from so far, but the reason for that is actually if you look at this peak around between 700 and 800, this peak actually is for magma magma. And as I said to you initially the surface oxidation lead to what the formation of what of magma so this is a big problem for preparing nanoparticles of magma as I said you magnetite. And then what you see here actually, as you do the materials and was increasing the concentration clearly that that peak does not enhance itself as before and as you can see diminishes and when you ratio X equal to point five, this means that high amount of magma is coming then there is no magma phase. And now clearly I can go back and look at why I have hematite. As I said to you, magma if you hate it becomes hematite and clearly, because here we are doing Raman's spectroscopy we're using laser source and was when you suppose the material to laser then the magma it will go to hematite. So the important thing that you can see from this data is that at high concentration of manganese, there will be hindrance of what of the formation of magmaite and you can say that the magnetite to magma transformation is what is hindered by cause of what because of this, this insertion of manganese in the structure. This is the most for that I'm not going to go into details but the conclusion from this data because in most where you can, you can, of course, look at the parameters and you can know which parameters go for magnetite and which for magmaite and so on. So our results actually for most portion of that for the pure material which is undocked then we have 70 to 30 ratio of magnetite to magma is even that 30% of our materials are transferred to magmaite. The other thing from. Okay, this is not only is only in the end of sample but the other one is not actually like that. So clearly for the sample with with x equal point five, there was no any transformation and all these peaks could be attributed to what to magnetite. The other thing that because the most for this actual I am most possible to copy, which tells you the amount of iron in both sides, a and V site and found that for the magnesium doped magnetite, the issue. Okay, the spectrum for the spectrum for what for the SI decreases us we conclude from that iron at the test that will be what will be replaced by what by by manganese to the other thing that the hyper fine parameters. And as much as the police splitting hyper fine mental field, all decrease because of this end of it. So I just go, and this is what I said before. Now what we done after that what we have done after that we tried to use x ready with the refinement and as you can see from this little refinement. You have two phases, you have magma it and magnetite and XRD shows you that the ratio is almost similar to that one extracted from the most for that which actually is another proof that magma might is always there whenever you have and the magnetite. And this is the structure which shows you the situation I'm not going to talk about this but actually this high resolution transition to make a study gives you information about whether you have magma it or not because you can find the enterprise XPS also has shown us when you have the pure material, there is no, if you look at the red curve, actually, the spectrum here is for iron two so I am to is very few actually in what in the surface of what of the pure sample which means that there has been an extension for what for to magma it but as you can see with increasing manganese content than the component for what for iron two becomes in large and clearly at the end this is what you expect I mean it should be one to two actually with the ferric ions. Okay, now this is the interesting part. We have done the refinement for what for the sample which is dobbies point five. I'm in and they as you can see we have only one phase which is a magnetite phase which is docked, but what's important here that as you can see the refinement shows you where the manganese iron go clearly they go to the head side where they have wanted to work for oxygens and as you can see here three and then both the site and one of the iron that has a set of heads that will be what will be expected well expect what to an interstitial site so this is a very interesting structure you have the MN ions going to tetrahedron sites and one MN will be removed from one site to what to an interstitial tetrahedron site as shown there. This is a magnetic data I'm not going to go in detail but here we can get the black and temperature I'm not going to go in detail because I don't have time but clearly we can get the black and temperature about which material okay shows the paramagnetic behavior and below it shows the magnetic behavior and clearly the black and temperature is decreasing with what was increasing ion concentration and the very transition which actually takes place at 120K in what in the bulk materials he actually is taking place in a very, very low temperature about 10 Kelvin. Okay, this is important actually this is a relation meditation that you can extract from the hysteresis loops and clearly with increasing MN content initially the amount of what or the meditation decrease and then eventually it decreased this is our model for that because this is for the pure material now. For the pure material as you said we have eight formulas per cell so this is the very simple model for what for the magnetization into unit cells and as you can see in the B site you have alignment up and then down in the A site and then what you expect here in this case for these two subletters you expect to have a difference of 64 bone magnitude. Now if you go to the model that we extracted from what from the most power and XRD as you can see here we said the three manganese iron we replace what we replace iron three at what the other side so this is just by the way they have the same spin so five. One magnet on for this and then the additional one now we put it also into the head side and because now the difference will be less. This is what you get here and that actually is consistent with what with the with defining that the meditation decreases initially after a while of course you are going to have more manganese and then when you have more manganese and. The site we expect a complex interaction with what with the ion three dipole moments and in that case one expect to have some sort of counting behavior, which makes the difference. Now larger because that's counting and what can decrease the conclusion of what of the asset monetization. Well, this is what we got and the behavior to see that the line is what we expect from what from the XRD or the most work defect model but this actually if you if you introduce your counting then you get to get this behavior. Okay, after that what we did we try to. To use automation just to check whether this fitting distribution of the curtains is right or not, we have five minutes. Okay, I'll try to finish it within this five minutes. Okay, so what you have see here what you see here that we have use the Gulf model or the model for the. For the optimization of these crystal is just backing home model where you have the column part and then you have this to turn for the polyterm and the short. Interaction 10. And these are the different models that we tried. So these are different scenarios that you assume that the defect can go to this side to the side and then you can see we had here. Got to defect model was the lowest possible energy in the first one, the one to the right. As you can see here, you have three manganese go to the head side as we found the in the experiment and also here you have in goes to the other side and transition, but the other one which is also shown here in brown, as you can see there, the, the energy is slightly less than that but actually this looks like the one that we have got experimentally so what we did we tried to just check this by by doing a DFT modeling and as you can see here we have turned a supercell from cubic because this calculation has done a lot of pressure and because of that because the lot of pressure structure is mono clinic. So we took the same models and put them here and just try to see which one is consistent with what we get. This is for the pure material as you can see on the on the line to have the density of the says where you, you have just above the family. Level you have a gap which is consistent with what we got from experiments and also the high profile parameters that we did measure from the most part are consistent with what you have here and now let us see which model actually is is better than the other. Okay, let's have to skip this part. And because this is the net performance you have for one minute on. And now this is more than number one where you have two manganese iron substituting for what for the head side and then the third goes to this side. This gives you, as you can see what's important here that now the, the band energy gets smaller. And I just show you this spot. Now the application actually increases which is actually not what we found there. The high profile parameters are consistent with the measurement and then we go for the other model where we found that three men substitute the data header sites and then one iron will be expelled expelled toward to the site. And here as you can see very interesting properties. The material becomes half metallic as you can see and the high profile parameters also show the same trend and what is important for us now is that the net money decreases here. And because of that we assume that this is the most appropriate what model for the structure. So in short, our work has shown that higher double concentration progressively suppress magnetite to magma transformation something important for industry. The best defective structure. For this material is that when I am in substitute exclusive for iron that the site associated with what was the expression of one iron. So this is a very iron to what to interstitial side to try the site. The monetization decreases with a constitution up to this value and then increase and then this was explained in terms of counting. And we also use at least simulation to to confirm the defective structure gain experimentally and finally the DFT predicted magnetic and hyperfine that are consistent with experiment and also show that this material is half metallic and I'm going to say this one but I believe it for people just read it and I should thank everyone for for being patient with me. And the last thing actually just to thank my my group and my colleagues and thank you very much indeed. Thank you. Thank you, Prof. Thank you very much. So, we have five minutes for the interaction. Let me start with one question on on the chat room. So from the DFT calculations, why, why you use it small supercell. That's a good question because, well, just to do with our computational you know facilities here we cannot go for for big ones but it will be interesting to go for a big one you're right. Do you have any any suggestion and I mean why you're asking this question, aren't you happy with this findings for example or or what. Musa Hussein, you can actually unmute yourself and ask the question. I don't know I'm actually I'm asking for the person who was asking. Okay, unmute and continue the interaction. Musa. Yes. In the meantime we can we can. I think I have problems hearing you again that same. As you might continue with with your question. Yeah, so my question is still on the supercell. Yes, one is actually small insights. So, I don't know. So what was your vacuum size in this calculation. What was I'm sorry I cannot hear you can you just say the question again because apparently you had a one by one supercell. Yeah, it was one one by one by two actually. Yeah, so well, are you looking at. Can I watch usually when you have a supercell you're looking at the, maybe something in one two directions, and then keeping the other one fixed so what was the plane that you use to do you say 001 or 110 plane or what. Sorry, I have a problem actually. I have a run to hear your question, because I think you can see there is some problem here. Some nice. Yeah, understand but then yeah with supercell calculations one by one is actually small for a calculation so that's that might not translate what you actually hope to achieve because there are several things that the supercell is not big enough, and you can have quantum systems with such supercells so yeah, maybe you can consider using a bigger supercell and then we try yes we try. I got your point yes. I mean we're using a limited you know competition facilities. Yeah, we have to go for a bit better one yes you're right. So if you do that you see that there'll be a lot of variations, because one by one is actually very small in my opinion. Yeah, it makes sense to me. Thank you. Okay, thank you. Yeah, I have a question I think I see my almost set part of it because I was quite curious about the size of the supercell. Can you put your video please. Yes, I did. Can you just raise your voice I have a problem actually in hearing actually. My video is on I think. So you are a Stefan. Okay, fine. I was expecting Musa. That's why I was asking for his video, please go ahead Stefan. Okay quickly. So it was about the impact of this supercell size that you use on the properties that are revealed by the defects, because as Sima is pointing out I think that they should be a relation to that and then I want to ask to quit. So are you going to work on other spinel structures like cobalt oxide or cobalt ferrite? Well, we are actually now working on YIG and hexaferite actually. Yeah, but it will be interesting to work on the other ones but since my PhDs now are working on hexaferite I just prefer now to concentrate on that but it will be interesting to see the other ones. I'm not sure if there is no enough work on that because what is interesting about magnetite is that I mean it can be used you know in medical industry and this is actually one of our interesting things because it is nontoxic and so on. But we have to find the specification so that we can work on that for much magnetite is something very useful to study because it has a list of application particularly if you want to use it as direct delivery and so on then it is very useful not toxic. I will talk about this one that have cobalt I'm not sure but it works right anyhow. Okay, so I will thank you very much. So I will ask all the presenters today's morning presenters to open the camera for actually for the discussion.