Peter's Blog: Nanophase Materials Science Research at the Oak Ridge National Laboratory

Peter's Blog: Nanophase Materials Science Research at the Oak Ridge National Laboratory

INTRODUCTION

Hello, I am Peter, a rising senior. This summer I am involved in two postdoctoral studies under an internship at the Oak Ridge National Laboratory. I encourage all of you to try it out because it offers a experience in a professional environment and a look into science academia (research, publishing, etc.) that cannot be found in a "program." That being said, my path getting here was a little different; you will probably need to have had participated in an internship in the past to be put in the applicant pool, since they generally take undergraduate and graduate students. At this level, work experience trumps grades and scores (good, because you won't have a college GPA), so if you have participated in an internship in the past I urge you to give it a shot.

WEEK 1

The first day was mostly going through the process of getting acquainted with things. I was assigned into a group under the Nanomaterials Theory Institute, part of the Center for Nanophase Materials Science. One of my first reactions was astonishment at the size of the laboratory campus, which occupies about 10,000 acres. CNMS is only one of 26 facilities at the laboratory. I also had to get used to the crazy amount of security protocol that was in place. Although none of my work concerned any military use, I still had to follow the procedures. It took me about an hour to get properly badged and cleared to even enter the facility.

There's a badge check just to get into the bathroom.

My work consists of two studies that are ongoing at the laboratory, one being the effects of partial La filling and Sb vacancies on CoSb3 skutterudites, and the other being the effects of stress-strain systems on the same materials. The proposals were granted by the Department of Energy for their use in alternative energy sources ­­— CoSb3 is is being researched as a potential low-cost thermoelectric material. In short, the two studies mostly consist of theoretical calculations based on experimentally observed electron energy energies and bands.

Almost immediately, I was also stunned by the researcher demographic. More than half of the laboratory researchers came from overseas; in fact, in both the postdoc study groups that I am a part of, we speak exclusively Mandarin Chinese. Another group in the same building, researching the applications and manufacturing of nanocarbon tubes, spoke some dialect of Hindi.

Oak Ridge National Laboratory, Department of NanoFIZZIX.

Before I did anything, I had a lot of information to catch up on, but I had already reading up on the information a while ago, when I had been notified about my acceptance, so it was not too bad. I suggest to everyone doing an internship to do so, even if the professor/mentor/higher-up does not say anything about it. If you go into your program and only start learning then, you will definitely miss out of getting the best experience out of it because you will always be struggling to catch up. Regardless, I was still pretty new to the computational and solid-state physics, a field very dense with calculus and obtuse multivariate functions.

I was also tasked with learning Fortran, and although I had a sizable knowledge of JAVA programming and other languages, I had never written low-level code. Fortran, even in its long history (60 years old!), is by no means archaic. Most computational and quantum physics programs rely on complex legacy libraries written in F77 or F90, and no one has bothered to rewrite them in any languages such as Python or C++ since, simply because of the speed that Fortran compiles and runs. Of course, that also means that sometimes simple operations take an enormous number of lines to express.

The important people in the institute get upstairs offices with cool floor-to-ceiling windows.

My first assignment as an intern was to sort through some electron data that needed to be checked before it was sent off for submission into Physical Review Letters. The .dat file was probably a couple hundred MBs large, which may seem pretty small at first, but it amounts to upwards of a billion rows of data. I accidentally opened the file in Excel and about 10 seconds later my computer BSODed.

It was only after my computer had crashed and rebooted from an overflow of data when one of the postdocs told me in broken English that all the computing was outsourced to the computational sciences division at the laboratory.

Bottom right: signed by Rick Perry, Al Gore; they visited ORNL and I missed them by only a couple weeks.

Pictured above is the Titan supercomputer. There is a running joke around the laboratory that the reason why it was built was so that when scientists from other national laboratories (who do not possess an on-site supercomputer) send their data over to be processed, ORNL researchers would screw with it.

The Titan supercomputer is one of three supercomputers at the lab, succeeding Jaguar. The third one, an IBM collaboration called Summit, is currently down for repairs. Our department (including other physics departments at the lab) is given permission to use some of the computing resources to run simulations and calculations.

Uploading and running the program worked extremely quickly, and the program I had written was able to process the data faster than the time it had taken to upload it. I was just glad that my program had even worked, as in order to meet a deadline I wasn't able to make my code organized. It ended up being around 500 lines of ugly compiler-error fixes and terrible indent formatting.

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In essence, the program reads input data over a specified Brillouin zone, analyzes the electron energy distribution and produces a Fermi-Dirac statistical distribution over the entire set of points. We can use that to check the measurements that were posted in the study. It turns out that there were a couple of precision errors as a result of rounding.

WEEK 2

I had my first hands-on experience. Part of the study requires the measurement of the conductance and valence bands of n- and p-type doped CoSb3, so we had to synthesize the intermediate to introduce La filling in the compound. To be honest, I had no idea what I was doing, but I just followed the instructions that my supervisor gave me.

Brillouin zone of a simple cubic lattice, with the sampling mesh points labeled.

The Brillouin zone can be calculated with relatively simple geometry with paper and pencil by tracing the altitudes of critical point half-lengths. There can be a variety of symmetries in a lattice, so there are also many different Brillouin zones that can be used, but generally the most regular ones are used.

After sampling across different k-points, using the Wannier90 program and our own written macros, we arrived with a large amount of data.

Joe's Blog - Working at Columbia Laboratory for Unconventional Electronics

jELLoo joSEf geAUx i do ENJOY studyin THOs ELEKTRIX