### material science

Computational Material Design – Quantum Engineering Laboratory, Engineering Physics, Institut Teknologi Bandung (discarded/unofficial) Logo

The hottest news I have had right now is about my experience in Japan last week! I had been given opportunity to visit Osaka University for two weeks as guest scientist and I am very grateful with the invitation. This time I was not going alone; there was another labmate who accompanied me so I (at least) wouldn’t feel lonely during my stay. For your information, in OU’s laboratory I visited there was a large number of Indonesians that were also former members of Computational Material Design – Quantum Engineering (CMD-QE) Laboratory of ITB. Since years ago, Kasai-Laboratory of OU (or let’s call it Handai because… why not!) and CMD-QE in ITB are best-buddies. We often share same topic of research, student exchange and last year doctoral student from Handai went back to our home country to be a teacher.

Summer Wars replica in Osaka Castle Museum

This was my second trip abroad, second trip to Japan, first time to Osaka, second time during Winter (because of the snowstorm you know you will meet snow even though it was Osaka), and second trip abroad in February. If you want some unimportant facts, this was also my first trip which transfer is Kuala Lumpur, Malaysia and second trip for academic purpose (which is a bit questionable). Before I forgot, these pictures are mine using Nokia N8 Camera.

OK, I’ll skip all the formalities and go for the content of the stay. We took off from Husein Sastranegara International Airport, Bandung, at February 3rd by AirAsia and arrived in Kansai International Airport, Osaka, about 11 PM Japan-Time. There wasn’t any transportation in the midnight so we went sleeping on 2nd Floor’s bench (which, according to the gossips, my senpais used the same spots each flight if they had to stay for a night – I thought we would be forced to rent a room in airport hotel, though… it is indeed cheaper this way). Unfortunately, I didn’t take lots of pictures this year unlike last year during my first visit. Most programs we had were workshops, seminaries and project meetings. I think I won’t share them here because they are unfinished projects. And of course I don’t have right to post anything without their permission.

Because all my Indonesian friends are Muslims and only I am the only Christian among them, I took liberty to eat almost anything without being worried about the content. If I compare the food in Osaka to Ishikawa back then, I will say Ishikawa wins this round. Part of it because we ate like, in restaurant, everyday back then but we need to buy anything on our own to-day. Osaka is known as city of snacks (nickname courtesy of my glutton friend) so even before I went there, I know what I want to eat:

Taiyaki bought in Mermaid Cafe at Kaiyukan Aquarium, Osaka

1. Takoyaki (even Hello Kitty Osaka edition’s costume is takoyaki)
2. Okonomiyaki (fuyunghai …I mean, like, omelet-like)
3. Issen Yoshoku in Kyoto (Kyoto’s original okonomiyaki)
4. Taiyaki (fish-shaped snack with red-beans filling inside)
5. Onigiri, Mochi, Ramen, Udon, Soba and junkfood including McD… (why are these on the list-)

Halal-food for Muslim friends is kinda rare here. Fortunately, there is Halal-dishes served in University’s canteen and Indian restaurant with Halal-Certificate. My friend always asked me to help him picking tuna-onigiri in supermarket because I can read Kana. Although rare, it is said that Japan is thinking of introducing Halal-food business nowadays since they also have tourists that came from Middle East. If you want to eat Osaka-snacks but are afraid if they are not Halal, I can recommend you Taiyaki (a fish-shaped cake with red-beans filling, no meat!), Okonomiyaki (but pick the vegetarian one), Issen Yoshoku (it is located in Kyoto near Gion Station and the list is in English, you can tell the chef to remove some ingredients you don’t like), Takoyaki (the filling is octopus). I don’t recommend Onigiri, Mochi, KitKat, Pocky or any snacks except MEIJI chocolates/ice-cream if you can’t read Kanji/Kana. For me, the only thing I won’t touch is wasabi.

Below read more is the list of places I’ve visited! There are few pictures each places, but – just enjoy!

I’m… surprised I haven’t written anything this month other than Happy New Year. I think I should have been more active in this site and learn how to write good opinion rather than yelling around, Ha! Let’s discuss something interesting before January ends. The background story comes from a nice chit-chat with my cousin and about my trip to Japan next month. I forgot what I talked about – I only remember I was talking non-stop about Japan and Osaka University and what I will do there in two weeks stay. Then here comes a good question from him: “What do you research?”

I explained briefly that I am going to design a material to improve rechargeable battery performance by computation method – using computers. Then he asked me something about “material design” and mentioned if I were to play God by creating new material. At an instant, I know what it means, but since he is not a physicist or scientist and (I know) he is not interested if I bring Schrodinger Equation or Quantum Physics there, I just put a wide grin and said, “Nope, just like what chemists do when they make drugs.” I hope my answer is quite clear, if not I don’t know what answer I should give.

In the eye of people, “nano-thingy” is related to “create a new material – and the One who has right to create material is God – so in other words, people who create new material is playing God.”

This statement often spurs from people not from this field. Nanoscience and nanotechnology is rather new for them and the implementation is very few compared to others. Yes, some countries have begun using nanotechnology for medical purpose, injecting sensors to monitor certain parameter inside our body like glucose or fighting cancer. But other than that, I think not that many. Ask people around you about thin film technology, SEM, TEM, spintronics, carbon nanotubes… and you may get questions rather than answer. It’s totally normal, although it had been developed since the birth of quantum physics in Einstein era, the theory itself is “strange and weird” in the first place. For example, electron is BOTH particle and wave. That alone is “weird”. And oh, even Microsoft Word and WordPress don’t recognize word for “nanoscience” and “spintronics”.

I should do this before I unconsciously turn this blog into photography-themed website..as I ‘ve promised, here I am to explain what I have got in Monte Carlo’s CASINO winter-school, or perhaps I should change the title into “How to gamble in CASINO properly”. Be careful, the rest of this article contains things behind human’s comprehension and in inhuman language.

Things that should be noted before I start explaining is the keywords to understand the method better: “DFT” (Density Functional Theory or to be more general; ab initio/ first principle, because we are working on Quantum Monte Carlo), “random walk” (random numbers ‘thrown’ into certain area of integration, a mathematical algorithm), Jastrow Factor (how can I not remember this thing), and the last is CASINO itself. I’ve had opportunity to meet and talk to the developers of this amazing computational program and was taught what was behind-the-program last month. Many of the courses filled with mathematics and algorithm rather than physical properties of a matter, and I honestly don’t want to include all things mathematical here or it’ll turn into one-lengthy-page-of-QMC-lecture. So be glad.

Quantum Monte Carlo was a very powerful method to compute a system, and has become quite a worldwide trend beside molecular dynamics. If QMC people are allowed to boast, it is more precise than DFT and 2-5% statistically closer to experimental. This ‘gambling’ method doesn’t need exchange correlation (as DFT’s basic and the source of the drift on Platinum to Gold system) and works in different way to solve Schrodinger Equation. In short, QMC excels DFT in term of accuracy and precision, because DFT isn’t that reliable.

That is the summary of the course and the reason why we need to learn about QMC. But unfortunately, my engineering-mind works in quite different way from my fellow scientists (alas, I’m the youngest, the only person who is still in undergrads, and in engineering field while people attending the course were mainly from Chemistry, Physics, or IT). I question what engineers usually ask:

“Is the method financially effective and efficient?”

QUE Project: Schrodinger
(click the image for larger resolution)

Schrodinger cat [here is a good site from Cornell Univ for your better understanding] is a very famous paradox cat in history (don’t take it seriously). Erwin Schrodinger gave this analogy to understand wave function in quantum physics – which sometimes people made a joke like comic strip above….. or so my labmates always said to our juniors to ‘scare’ them in quantum physics course lol.

QUE Project and all of the characters are belong to VnyX (me)

This is requested by lazy Listra. Here’s short resume for what Cica had shared yesterday at lab meeting. Will not give any clear details, though. You can read Griffith (Introduction to Quantum Mechanics), papers, or DFT references for further understanding – and oh, beware of alien language. There are at least 3 methods of modelling, those are:

ab initio [ Density Functional Theory ] —-> Tight Binding —-> Molecular Dynamics

the ab-initio only sees atoms and molecular dynamics involves molecules and over 10,000 atoms in simulation. Tight binding is the bridge between them. I will cover Molecular Dynamics sometime later, but here goes the flowchart of density functional theory.

Schrodinger —> Born-Oppenheimer —> Hohenberg-Kohn —> Kohn-Sahm —> Slater Determinant

1. Schrodinger: $i\hbar\frac{\partial}{\partial t}\left|\Psi(t)\right>=H\left|\Psi(t)\right>$ or simply $H\Psi = E\Psi$ with H is Hamiltonian and E is Total Energy. Schrodinger equation can’t be solved manually for many-body problems except for Hydrogen atom. We know that the Hamiltonian H is Kinetic Energy + Potential Energy . While $E_k = \frac{-\hbar^2}{2m_i}\frac{d^2}{dr^2}$ and $E_p = coulomb forces=\frac{1}{4 \pi \epsilon_0}\frac{qQ}{(R_i-r_i)}$
2. Born-Oppenheimer: assumption that the position of atomic nuclei constant because the mass of nuclei is about 2000x of electron. So the total energy can be reduced. The Kinetic Energy of nuclei equals to zero so we only get the combination of kinetic energy of each electrons added by combination of coulomb forces potential energy between particles.
3. Hohenberg-Kohn: remember pool of water. This contains one-one correlation. The density of electron “n” is unique for certain wave function only on the ground state condition. For example $\Psi_1 = n_1 (x); \Psi_2 = n_2 (x)$ and etc.
4. Kohn-Sahm: about the complexity of wave function and involve exchange correlation. The schrodinger equation before Kohn-Sahm is $(E_k + V_{effective} + V_{exchange correlation})\Psi = E\Psi$ where $\Psi(r_1, r_2, ..., R_1, R_2, ...)$. Exchange correlation is used because each electron, unlike nuclei, is indistinguishable. With Kohn-Sahm, we approach the equation by stating that there is no interaction between particles, so that $\Psi(r_1, r_2, ..., R_1, R_2, ...) = \Psi(r_1) \Psi(r_2) ...$

QUE Project: C-sama
(click the image for larger resolution)

You who have learned basic chemistry must have known. Carbon is an element, but it has two pure stable structure that you can find in Mother nature: GRAPHITE and DIAMOND. While their element is the same, Carbon, the structure difference makes big difference in material behavior and characteristics. Diamond – well, who know not this beaut – has atomic structure like silica, it is sturdy, the strongest material and only diamond can cut diamond, beautiful, transparent and the most important thing is…expensive. and hard. Graphite? Cheap, black, the structure is layered hexagonal and brittle, because it’s inert and cheap it is usually used as electrodes.

Humans and all beings are composed (mainly) of CARBON. It’s a strange material that (invades earth – joking) can be combined to many (strange) structures such as polymer, carbon nano tube, organic material, etc. Since its abundance and usefulness, research on Carbon is quite popular among scientists.

QUE Project and all of the characters are belong to VnyX (me)

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