Tag: science communication

Colloquium on Porous Frameworks: Day 1

Program Porous Frameworks ColloquiumToday the CMD26 conference started in Groningen, and with its kick-off also our own 2-day colloquium on porous frameworks (aka MOFs, COFs and Zeolites) was launched. During the two sessions of the day, the focus mainly went out to the Zeolites, with Prof. Emiel Hensen of the Technical university of Eindhoven introducing us to the subject and discussing how new zeolites could be designed in a more rational way. He showed us how the template used during synthesis plays a crucial role in the final growth and structure. Dr. Nakato explained how alkali-metal nanoclusters can undergo insulator to metal transitions when incorporated in zeolites (it is due to the competition between electron-electron repulsion and electron-phonon coupling), while Dr. De Wijs informed us on how Al T-sites need to be ordered and assigned in zeolites to allow for the prediction of NMR parameters.

After the coffee break Dr. Palcic, from the Rudjer Boskovic Institute in Croatia, taught us about the role of heteroatoms in zeolites. She told us that even though more than 2 million theoretical structures exist, only 231 have officially been recognized as having been synthesized, so there is a lot more work to be done. She also showed that to get stable zeolites with pores larger than 7-8 Angstrom one needs to have 3 and 4-membered rings in the structure, since these lead to more rigid configurations. Unfortunately these rings are themselves less stable, and need to be stabilized by different atoms at the T-sites.

Dr. Vandichel, still blushing from his tight traveling scheme, changed the subject from zeolites to MOFs, in providing new understanding in the role of defects in MOFs on their catalytic performance. Dr. Liu changed the subject even further with the introduction of COFs and showing us how Hydrogen atoms migrate through these materials. Using the wisdom of Bruce Lee :

You must be shapeless, formless, like water. When you pour water in a cup, it becomes the cup. When you pour water in a bottle, it becomes the bottle. When you pour water in a teapot, it becomes the teapot.

he clarified how water behaves inside these porous materials. Our first colloquium day was closed by Ir. Rohling, who took us back to the zeolite scene (although he was comparing the zeolites to enzymes). He discussed how reactivity in zeolites can be tweaked by the confinement of the reacting agents, and how this can be used for molecule identification. More importantly he showed how multiple active site collaborate, making chemical reactions much easier than one would expect from single active site models.

After all was said and done, it was time to relax a little during the conference welcome reception. And now time to prepare for tomorrow, day 2 of our colloquium on porous frameworks.

 

Holiday-Conference roller coaster

Visit to Stockholm. The knight at the Medeltidsmuseet (top left), brown bear in Skansen (top right), visiting the Royal palace (bottom left) and local entertainment in the old city center (bottom right).

Visit to Stockholm. The knight at the Medeltidsmuseet (top left), brown bear in Skansen (top right), visiting the Royal palace (bottom left) and local entertainment in the old city center (bottom right).

Summertime is a time of rest for most people. For our little academic family, last summer was a bit of a roller coaster; alternating holidays with hard work which had been postponed too much. The last vestige of my start of a new chapter (moving the remaining stuff from the apartment to our house) was finally bested. Now the conference roller coaster has started with Sylvia’s plenary lecture on conceptual spaces in Stockholm.

As neither of us ever visited Sweden before, we decided to turn it into a semi-family-holiday as well. Our 4-year-old son enjoyed his first ever plane flight (he wasn’t really convinced something impressive was going on). And while Sylvia was of to the conference, the two of us went to explore Stockholm: Finding the knight in the Medeltidsmuseet (at the left in the back of this beautiful museum 🙂 ) and searching for the king and queen at their palace (they weren’t there 🙁 ). Or visiting one of the oldest open-air musea; Skansen (similar to Bokrijk in Belgium) where we saw old professions at work (making cheese for example) and native Scandinavian farm and wild animals (from peacocks to brown bears).

Next weekend starts the next episode of the conference roller-coaster with me hosting a 2-day colloquium on porous frameworks together with Bartek Szyja and Ionut Tranca at the CMD-26 conference in Groningen. We have a nicely packed colloquium with about 20 presentations (8 invited and 12 contributed) covering the whole realm of porous materials from zeolites to COFs and MOFs. The program of the colloquium can be downloaded below:Program Porous Frameworks Colloquium

I have a Question: about thermal expansion

“I have a question”(ik heb een vraag). This is the name of a Belgian (Flemisch) website aimed at bringing Flemisch scientists and the general public together through scientific or science related questions. The basic idea is rather simple. Someone has a scientific question and poses it on this website, and a scientist will provide an answer. It is an excellent opportunity for the latter to hone his/her own science communication skills (and do some outreach) and for the former to get an good answer to his/her question.

All questions and answers are collected in a searchable database, which currently contains about fifteen thousand questions answered by a (growing) group of nearly one thousand scientists. This is rather impressive for a region of about 6.5 Million people. I recently joined the group of scientists providing answers.

An interesting materials-related question was posed by Denis (my translation of his question and context):

What is the relation between the density of a material and its thermal expansion?

I was wondering if there exists a relation between the density of a material and the thermal expansion (at the same temperature)? In general, gasses expand more than solids, so can I extend this to the following: Materials with a small density will expand more because the particles are separated more and thus experience a small cohesive force. If this statement is true, then this would imply that a volume of alcohol should expand more than the same volume of air, which I think is puzzling. Can you explain this to me?

Answer (a bit more expanded than the Dutch one):

Unfortunately there exists no simple relation between the density of a material and its thermal expansion coefficient.

Let us first correct something in the example given: the density of alcohol (or ethanol) is 46.07 g/mol (methanol would be 32.04 g/mol) which is significantly more than the density of air which is 28.96 g/mol. So following the suggested assumption, air should expand more. If we look at liquids, it is better to compare ethanol (0.789 g/cm3) to compare water (1 g/cm3) as liquid air (0.87 g/cm3) needs to be cooled below  -196 °C (77K). The thermal expansion coefficients of wtare and ethanol are 207×10-6/°C and 750×10-6/°C, respectively. So in this case, we see that alcohol will expand more than water (at 20°C). Supporting Denis’ statement.

Unfortunately, these are just two simple materials at a very specific temperature for which this statement is true. In reality, there are many interesting aspects complicating life. A few things to keep in mind are:

  • A gas (in contrast to a liquid or solid) has no own boundary. So if you do not put it in any type of a container, then it will just keep expanding. The change in volume observed when a gas is heated is due to an increase in pressure (the higher kinetic energy of the gas molecules makes them bounce harder of the walls of your container, which can make a piston move or a balloon grow). In a liquid or a solid on the other hand, the expansion is rather a stretching of the material itself.
  • Furthermore, the density does not play a role at all, in case of the expansion of an ideal gas, since p*V=n*R*T. From this it follows that 1 mole of H2 gas, at 20°C and a pressure of 1 atmosphere, has the exact same volume as 1 mole of O2 gas, at 20°C and a pressure of 1 atmosphere, even though the latter has a density which is 16 times higher.
  • There are quite a lot of materials which show a negative thermal expansion in a certain temperature region (i.e. they shrink when you increase the temperature). One well-known example is water. The density of liquid water at 0 °C is lower than that of water at 4 °C. This is the reason why there remains some liquid water at the bottom of a pond when it is frozen over.
  • There are also materials which show “breathing” behavior (this are reversible volume changes in solids which made the originators of the term think of human breathing: inhaling expands our lungs and chest, while exhaling contracts it again.) One specific class of these materials are breathing Metal-Organic Frameworks (MOFs). Some of these look like wine-racks (see figure here) which can open and close due to temperature variations. These volume variations can be 50% or more! 😯

The way a material expands due to temperature variations is a rather complex combination of different aspects. It depends on how thermal vibrations (or phonons) propagate through the material, but also on the possible presence of phase-transitions. In some materials there are even phase-transitions between solid phases with a different crystal structure. These, just like solid/liquid phase transitions can lead to very sudden jumps in volume during heating or cooling. These different crystal phases can also have very different physical properties. During the middle-ages, tin pest was a large source of worries for organ-builders. At a temperature below 13°C β-tin is more stable α-tin, which is what was used in organ pipes. However, the high activation energy prevents the phase-transformation from α-tin to β-tin to happen too readily. At temperatures of -30 °C and lower this barrier is more easily overcome.This phase-transition gives rise to a volume reduction of 27%. In addition, β-tin is also a brittle material, which easily disintegrates. During the middle ages this lead to the rapid deterioration and collapse of organ-pipes in church organs during strong winters. It is also said to have caused the buttons of the clothing of Napoleon’s troops to disintegrate during his Russian campaign. As a result, the troops’ clothing fell apart during the cold Russian winter, letting many of them freeze to death.

 

 

Annual Meeting of the Belgian Physical Society 2016

ConferenceLogoWebsite_1

Wednesday May 18th was a good day for our little family. Since my girlfriend an I both are physicists by training, we attended the annual meeting of the Belgian Physical Society in Ghent, together. What made this event even more special was the fact that both of us had an oral presentation at the same conference, which never happened before. 🙂

Sylvia talked about an example of indeterminism in Newtonian mechanics, and showed how the indeterminism can be clarified by using non-standard analysis. The example considers the Norton Dome, a hill with a specifically designed shape ( y(x)=-2/3(1-(1-3/2|x|)^{2/3})^{3/2} ). When considering a point mass, experiencing only gravitational force, there are two solutions for the equation of motion: (1) the mass is there, and remains there forever (r(t)=0) and (2) the mass was rolling uphill with a non-zero speed which becomes exactly zero at the top, and continues over the top (  r(t)=\frac{1}{144} (t-T)^4 with T the time the top is reached). Here, r refers to the arc length as measured along the dome (0 at the top). In addition, there also exists a family of solutions taking the first solution at t<T, while taking the second solution at t>T. (As the first and second derivatives of these latter solutions are continuous, Newton will not complain.) This leads to indeterminism in a Newtonian system; for instance, you start with a mass on the top of the hill, and at a random point in time it starts to roll off without the presence of an external something putting it into motion. Using infinitesimals, Sylvia shows that the probability for the mass to start rolling off the dome immediately is infinitesimally close to one.

My own talk was on the use of computational materials science as a means for understanding and explaining experimental observations. I presented results on the pressure-induced breathing of the MIL-47(V) MOF, showing how the experimentally observed S-shape of the transition-pressure-curve can be explained by the spin interactions of the unpaired vanadium-d electrons: it turns out that regions with only ferromagnetic chains compress already at 85 MPa, while the addition of higher and higher percentages of anti-ferromagnetic chains increases the pressure at which the pores collapse, up to 125 MPa for the regions containing 100% anti-ferromagnetic chains. As a second topic, I showed how the electronic band structure of the linker-functionalized UiO-66(Zr) MOF changes. When one or two -OH or -SH groups are added to the benzene ring of the linker, part of the valence band is split off and moves into the band gap. In semiconductors, this would be called a gap state; however, in this case, since every linker in the material contributes

Belgian Physical Society Meeting 2016

Top left: I am presenting computational results on MOFs. Top Right: Sylvia presents the Norton Dome. Bottom: Group picture at the central garden in “Het Pand”. (Photos: courtesy of Sylvia Wenmackers (TL), Philippe Smet (TR), and Michael Tytgat (B) )

a single electron state to this gap state, it practically becomes the valence band top. As a consequence, the color of such functionalized MOF’s changes from white to yellow and orange. As a third topic, I discussed the COK-69(Ti) MOF. In this MOF the electrons in the titaniumoxide clusters are strongly correlated, just as for pure titaniumoxide. Because such systems are poorly described with standard DFT, we used the DFT+U approach, which allowed us to discern between Ti3+ and Ti4+ ions. The latter was practically done by partitioning the electron density using the Hirshfeld-I scheme.

Next to our own talks, the BPS-meeting started with two very interesting plenary lectures on the two big machines/facilities of the physics community: ITER (fusion reactor under construction) and LHC (circular collider, under constant upgrade) at CERN. Prof. Jean Jacquinot, presented the progress in fusion research (among which simulations of plasma-instabilities) and the actual building progress of the ITER facility. Prof. Sergio Bertolucci on the other hand informed us on the latest results obtained with the LHC at CERN, but also about future plans (Future Circular Collider, with a circumference of about 100 km!!). He also showed us the amount of data involved in running the CERN experiments, puting them into perspective: LHC produced in 2012 about 15 Petabyte of data per year (15.000 Terabyte) which is the same as the mount of data added to Youtube on yearly basis. At that time the ATLAS experiment had a dataset of 140 Petabyte (compare to the 100 Petabyte of google’s search index or the 180 Petabyte of facebook uploads/year). The presenters, both excellent and enthusiastic speakers, reminded us that these projects thrive on the enthusiasm of young researchers with open minds. But they also noted, something that is rather often forgotten, that it is the journey not the goal which is most important. Of course, ITER is the next step on the road to commercial fusion power, but along the way much more is learned as a result of tackling practical problems. This is even more so for the CERN experiments, where the “goal” is not as related to our daily lives (keeping the lights on) but focuses on understanding the world. This is at the core of what it means to be a physicist: the need and drive to understand the world. This is also what should drive research but becomes increasingly hampered by the funding-question: how/what profit will it make in the “real world”. Remember the transistor which makes your computer and smartphone as powerful as they are, the laser in CD/DVD-players, the internet allowing you to read this post, and so many more.

Following these plenary presentations, four young scientists competed for the young speaker award presenting their PhD research. Two presentations (1),(2) focused on vortices in superconductors, a third one discussed the use of plasmons in graphene nanoribbons to enhance telecommunication while the fourth talk introduced us into the world of string theory.

In the afternoon, there were six parallel session, of which I mainly attended the Condensed Matter and Nanostructure Physics-session (since I had my own talk there) and the Biological, Medical, Statistical and Mathematical Physics-session rooting for Sylvia. During the Condensed matter session I was mainly fascinated by the presentation of Prof. Sara Bals, on coloring atoms in 3 dimensions. She showed how, using energy-dispersive X-ray (EDX) mapping it is possible to create a 3D atomic lattice of nano-materials and clusters. This is a more direct approach than the usual X-ray diffraction (XRD) approach for identifying a crystal structure. Unfortunately, I am afraid this technique may not be well suited for the MOFs I’m working on, since they contain mainly light elements and not heavy metals(although it may be interesting to try once the technique is optimized further). It is, however, definitely a technique to remember for future projects, to suggest to experimental collaborators.

Links:

Call for Abstracts: Condensed Matter Science in Porous Frameworks: On Zeolites, Metal- and Covalent-Organic Frameworks

Flyer for the Colloquium on Porous Frameworks at the CMD26Together with Ionut Tranca (TU Eindhoven, The Netherlands) and Bartłomiej Szyja (Wrocław University of Technology, Poland) I am organizing a colloquium “Condensed Matter Science in Porous Frameworks: On Zeolites, Metal- and Covalent-Organic Frameworks” which will take place during the 26th biannual Conference & Exhibition CMD26 – Condensed Matter in Groningen (September 4th – 9th, 2016). During our colloquium, we hope to bring together experimental and theoretical researchers working in the field of porous frameworks, providing them the opportunity to present and discuss their latest work and discoveries.

Zeolites, Metal-Organic Frameworks, and Covalent-Organic Frameworks are an interesting class of hybrid materials. They are situated at the boundary of research fields, with properties akin to both molecules and solids. In addition, their porosity puts them at the boundary between surfaces and bulk materials, while their modular nature provides a wealthy playground for materials design.

We invite you to submit your abstract for oral or poster contributions to our colloquium. Poster contributions participate in a Best Poster Prize competition.

The deadline for abstract submission is April 30th, 2016.

The extended deadline for abstract submission is May 14th, 2016.

 

CMD26 – Condensed Matter in Groningen is an international conference, organized by the Condensed Matter Division of the European Physical Society, covering all aspects of condensed matter physics, including soft condensed matter, biophysics, materials science, quantum physics and quantum simulators, low temperature physics, quantum fluids, strongly correlated materials, semiconductor physics, magnetism, surface and interface physics, electronic, optical and structural properties of materials. The scientific programme will consist of a series of plenary and semi-plenary talks and Mini-colloquia. Within each Mini-colloquium, there will be invited lectures, oral contributions and posters.

 

Feel free to distribute this call for abstracts and our flyer and we hope to see you in Groningen!

Virtual Winterschool 2016: Computational Solid State Physics & Chemistry

In just an hour, I’ll be presenting my talk at the virtual winterschool 2016. In an attempt to tempt fate as much as possible I will try to give/run real-time examples on our HPC in Gent, however at this moment no nodes are available yet to do so. Let’s keep our fingers crossed and see if it all works out.

Abstract

Modern materials research has evolved to the point where it is now common practice to manipulate materials at nanometer scale or even at the atomic scale (e.g. Intel’s skylake architecture with 14nm features, atomic layer deposition and surface structure manipulations with an STM-tip). At these scales, quantum mechanical effects become ever more relevant, making their prediction important for the field of materials science.

In this session, we will discuss how advanced quantum mechanical calculations can be performed for solids and indicate some differences with standard quantum chemical approaches. We will touch upon the relevant concepts for performing such calculations (plane-wave basis-sets, pseudo-potentials, periodic boundary conditions,…) and show how the basic calculations are performed with the VASP-code. You will familiarize yourself with the required input files and we will discuss several of the most important output-files and the data they contain.

At the end of this session you should be able to set up a single-point calculation, a structure optimization, a density of states and band structure calculation.

Additional Files/Info

Winterschool on computational chemistry

Starting next week from February 3rd up to February 9th the second virtual winterschool on computational chemistry will take place. This week-long winter school is packed with interesting webinars given by experts from all over the world (among others Kieron Burke and John Perdew, jep those of the DFT-functionals we are using) and me. I’ll be presenting an introductory tutorial in solid state calculations and how to use VASP for this task.

Registration for this winter school is free, and since it takes place on the world wide web, there is still room at the back :-). (In addition to a lack of worries whether or not you will be able to get your hands on a last minute plane-ticket or hotel-room and which funding agency might reimburse those tickets.) I’ll be running example-calculations real time, and hope my sidekick will perform to expectation.

Robbert Dijkgraaf Essay Contest

In the previous posts, I presented my contribution (original Dutch version / English translation) to the Robbert Dijkgraaf essay contest. This year’s theme was on the importance of imagination in science. My girlfriend, Sylvia, also participated in this essay contest. We read each-others contributions as a final check before submission, and at that point it became clear to me I was out of my league 😳 .

During the gala of science in Amsterdam, the winner of the Robbert Dijkgraaf essay contest was made public. And the winner is: Sylvia Wenmackers.

On her blog you can read the winning essay (in Dutch), and you will understand why I immediately knew my essay was outclassed. Congratulations again my dear 😀 .

 

 

Sidekick

This year I participated in the Robbert Dijkgraaf essay-contest 2015.
The central theme of the contest was imagination, and in my contribution
I presented the role of imagination in computational materials science,
and why it is so important for this field

The original Dutch version of the essay can be found here.

 

Imagine a world where you can actually see atoms. Even more, you can use them as LEGOs and manipulate them to do your bidding. Imagine a world in which you can switch off the laws of nature, or create new ones which are more to your liking. In such a world, you are in charge. Welcome to my world: the world of “computational materials science“.

It would be a nice start for a commercial for this research field. The accompanying clip would then show images fading into one another of supercomputers and animations of chemical and biochemical processes at the atomic scale. Moving in a fast-forward pace into our future with science-fiction-like orbital labs where calculated materials are immediately transformed into new medicine, ultra-thin screens and applications for the aerospace industry. scifilabThe ever faster flood of images culminates in the final slogan:”Simulate the future” with a subtext urging you to go study computational materials science. I assume that such a clip would tempt peoples imagination. It addresses our human urge to create, and holds the promise that you can do anything you want, as long as you can imagine it. In fact, your imagination becomes the only limiting factor.

As with most commercial, this one also presents reality slightly more beautiful than it actually is. As for any other scientist in any other field, your contribution to progress as a computational materials scientist is rather more limited than you would like it to be. This is a normal aspect of science. The presented divine omnipotence and omniscience, on the other had, are attainable. As a computational scientist you do have absolute control over the atomic positions and the forces at play. In contrast, an experimental scientist is forced to deal with the quirks of nature and his or her machinery. This omnipotence allows you to create any world you can imagine…inside a computer.

As a scientist, you wish to understand the world around you. This limits the freedom you gained through your omnipotence, unless you would choose to join a team of game-designers. It, however, does not mean that your creativity is curtailed in any way. On the contrary. Where the team of game-designers knows the entire story to be told, including rules and laws of nature relevant for the game world, this is not the case for computational materials science. For the latter it is often their quest to discover the story-line as they go, including relevant laws of nature. As a computational materials scientist, you become the narrator, whose task consist of thinking up new stories time and time again. The narrator, who needs to tweak existing plots, extending or confining story-lines, until the final story fits the shape of reality.

Luckily, you are not alone to bring this daunting task to a successful end. You always have the support of your loyal sidekick: your supercomputer. Using its brute force, your sidekick calculates the effects of any intrigue or plot twist you can imagine. Based on your introductory chapter, in which you describe the world and its natural laws, it will allow the story to unfold. By asking him the right questions, and comparing his answers to reality, you learn which parts of your story don’t really fit reality yet.

Ouroboros benzene. source: wikipediaHow you should rewrite your introductory chapter differs every time. Sometimes it is clear what is going on: an essential character is missing (e.g. an impurity atom which is distorting the crystal lattice), or the character lives at the wrong location (not site A, then let us see about site B?). It becomes more difficult when a character refuses to play the role it was dealt (e.g. Pt atoms that remain invisible for STM, so who is going to play the role of the nanowire we observe?). The most difficult situation occurs with the need for a full rewrite of the introductory chapter. This provides too much freedom, since it is our knowledge of the limitations of reality which provides the necessary support and guidance for drafting the story-line. In such a case, you need an inspiring idea which provides you with a new point of view. Inspiration can come in many forms and at any time, often when least expected. A well-known example is this of the theoretical chemist Kekulé who, in a daydream, saw a snake bite its own tail. As a result Kekulé was able to envision the ring-shape of the benzene molecule. Such wonderful problem solving twists-of-mind are rare. They are often the consequence of long and intense study of a single problem, which drive you to the limit, since they require you to imagine something you have never thought of before. In management-circles this is called “thinking-outside-the-box”, which sound a lot easier than it actually is. It does not mean that all of the sudden everything goes, you always have to bear in mind the actual box you started from.

As a computational materials scientist you have to combine your omnipotence over your virtual world with your power to imagine new worlds, hoping to see a glimmer of reality in the reflections of your silicon chips.

Sidekick

Met dit essay nam ik deel aan de Robbert Dijkgraaf essay-prijs 2015.
Dit jaar was het thema verbeelding, en in mijn bijdrage doe ik een
poging de rol van verbeelding naar voren te brengen binnen
computationeel materiaalonderzoek. Ik probeer eveneens uit te
leggen hoe ik computationeel onderzoek zie als onderzoeksdomein. 

Een vertaling naar het Engels kan hier gevonden worden.

 

Stel je een wereld voor waarin je atomen kunt zien. Meer nog, je kunt ze stapelen als legoblokken en manipuleren naar eigen goeddunken. Stel je een wereld voor waarin je de natuurwetten kunt aan- of afzetten, een wereld waar je zelf nieuwe natuurwetten kunt schrijven. In zo een wereld heb jij het voor het zeggen. Welkom in mijn wereld, de wereld van het “computationele materiaalonderzoek“.

Het zou een mooi begin zijn van een reclamespot voor dit onderzoeksgebied. In de bijhorende clip krijg je in elkaar overgaande beelden te zien van supercomputers enerzijds en animaties van chemische en biochemische processen op de atomaire schaal anderzijds. Het geheel wordt dan doorgelinkt aan onze eigen toekomst met sciencefictionachtige laboratoria waar de berekende materialen direct worden omgezet tot nieuwe medicijnen, flinterdunne beeldschermen en toepassing voor de ruimtevaart. De steeds sneller elkaar opvolgende beelden scifilabculmineren dan in de slotslogan: “Simuleer de toekomst!” met als onderschrift de aansporing om computationeel materiaalonderzoek te gaan studeren. Ik stel me voor dat zo’n reclameclip wel tot de verbeelding zou spreken. Het spreekt onze menselijke drang om te creëren aan met de belofte dat je alles kunt, als je het je maar kunt voorstellen. Je verbeelding is de enige beperkende factor.

Zoals bij de meeste reclamespots wordt ook in deze de werkelijkheid iets mooier voorgesteld dan ze is. Zoals voor elke andere wetenschapper geldt immers dat je bijdrage aan de vooruitgang beperkter is dan je zou willen. De gepresenteerde goddelijke almacht en alwetendheid liggen wel binnen handbereik. Als computationeel onderzoeker heb je immers absolute controle over de plaatsing van atomen en de inwerkende krachten, iets waar een experimenteel onderzoeker deels is overgelaten aan de grillen van de natuur en zijn of haar apparatuur. Deze controlevrijheid laat je toe, binnen een computer, elke wereld te creëren die je maar kunt bedenken.

Als wetenschapper wil je de wereld om je heen begrijpen, wat bovenstaande vrijheden inperkt, tenzij je ervoor kiest om in een team van computergame-designers aan de slag gaan. Dit betekent niet dat je creativiteit wordt beknot, integendeel. Waar bij het ontwerpteam het volledige verhaal bekend is, inclusief de regels en natuurwetten van de wereld waarin je speelt, is dat niet het geval bij computationeel materiaalonderzoek. Meer nog, vaak is het net je opdracht het verhaal gaandeweg te ontdekken, inclusief de natuurwetten die relevant zijn. Je wordt als het ware een verteller die telkens nieuwe verhalen moet bedenken, of bestaande plots moet aanpassen, uitbreiden of beperken, tot de verhaallijn past in de vorm van de werkelijkheid.

Je staat er gelukkig niet alleen voor om een goede afloop te regelen. Je wordt bijgestaan door je trouwe sidekick: je supercomputer. Deze is in staat met brute kracht de gekste plotwendingen door te rekenen. Op basis van jouw inleidende hoofdstuk, waarin je de wereld en haar natuurwetten schetst, zal hij het verhaal verder laten ontplooien. Door dan de juiste vragen te stellen en de antwoorden met de werkelijkheid te vergelijken kom je erachter waar je verhaal nog niet helemaal in de werkelijkheid past.

Hoe je je inleidende hoofdstuk daarop moet aanpassen verschilt per geval. Soms is het duidelijk wat er aan de hand is: er ontbreekt een cruciaal personage (bijvoorbeeld een onzuiverheidsatoom dat het kristaalrooster verstoord) of het personage woont op de foute plaats (toch niet op de plaats van atoom A, atoom B dan maar?). Moeilijker wordt het als sommige personages weigeren de hun toebedeelde rol te spelen (Die platina-atomen zijn onzichtbaar voor de rastertunnelmicroscoop, wie speelt nu de rol van de zichtbare nanodraad?).Ouroboros benzene. source: wikipedia De lastigste situatie is wanneer een volledige herschrijving van het inleidende hoofdstuk nodig is. Hierdoor krijg je te veel vrijheid in handen, terwijl het net de gekende beperkingen zijn die je houvast geven bij het opstellen van het verhaal. Je hebt dan een idee nodig dat je een link geeft met de werkelijkheid. Inspiratie kan hier velerlei vormen aannemen en op willekeurig moment komen. Een bekende anekdote is deze van de theoretische chemicus Kekulé, die in een dagdroom een slang zichzelf in de staart zag bijten en daardoor de ringvormige structuur van de benzeenmolecule uitdokterde. Zulke wonderlijk probleemoplossende gedachtenkronkels komen zelden spontaan, maar zijn veeleer het gevolg van lang en intens werk op eenzelfde vraagstuk. Dergelijke situaties drijven je tot het uiterste, je moet je immers iets voorstellen waar je nooit eerder aan gedacht hebt. In managementkringen wordt zoiets “buiten het kader denken” genoemd, wat bedrieglijk eenvoudig klinkt. Je mag immers niet vergeten dat voor onderzoek dit niet betekent dat alles plots toegelaten is (met andere woorden, je mag het kader zeker niet uit het oog verliezen bij het dagdromen).

Als computationeel materiaalonderzoeker moet je dus je almacht over je virtuele wereld combineren met je eigen vermogen nieuwe werelden in gedachten te scheppen, in de hoop zo onderweg een glimp van de buitenwereld in je siliciumchip op te vangen.