One of the goals of the course is to become familiar with modern computational software that solve difficult problems in solid state physics. You will use the software package Burai with Quantum Espresso to calculate the band structure of a semiconductor, metal, or insulator. You can complement your own calculations by downloading band structures from an open source project called AFLOW (https://www.aflowlib.org/search/ , search by element).
Decide on an interesting system (talk to the instructor and others about what is feasible). You always start by reproducing the work of others, and then go on to explore by yourself. You will calculate (at minimum for a passing grade) the dispersion relation and the total and partial densities of states of an interesting material. The difficulty of the project will be taken into account in assigning the grade, in difficult cases, dicsuss your "other property" by existing calculation form AFLOW (https://www.aflowlib.org/search/) or the Materials Project Database.
Summarize your results as a poster to be shown during class (date will be posted on the main calendar of the course). This is a conference of your peers, and may also be attended by interested parties such as former and prospective PH575 students, and faculty.
OSU Student Media Services, located in the Valley Library, prints posters for free if it is a class assignment. A typical poster size is 3 feet wide, 3.5 - 4 feet tall. Text and diagrams should explain your calculations, and provide other information about your material. During the poster session, you'll stay with your poster for 50% of the time, and circulate around other posters for 50% of the time. Some example posters (at all grade levels, password protected).
Posters should be uncluttered, informative and visually appealing.
Audience: You are writing a scientific article for an audience of your peers, e.g. incoming PH575 students. You and your peers are highly educated, technically savvy people, but you do not know everything about every material that has ever been discovered. You are educating your peers about a particular material that is of scientific interest or technological importance and you want to convey what is interesting or important about that material from the point of view of a scientist. You are all capable of reading and understanding articles in any of the journals on solid state physics or materials.
Here are some ideas that might stimulate your creativity
Are collaborations allowed ? Teach each other about how use QuantumEspresso basics. Share tips on how to use the software, especially on how to get to the DoS and the E(k) plots. This just like being in a lab where you show someone how to use a piece of equipment. This kind of collaboration is healthy, but don't do the work for the other person. In a lab, you show someone a tool and he or she decides what experiment to do with it.
Please do not perform the other person's calculation. Don't work together to construct your posters - the temptation to produce the same format is very strong. This is your poster. But critique someone's poster and offer advice if asked. Tell each other where to get poster materials or how to get access to good printing etc.
Posters EIther print full poster at library or use 8.5” by 11” sheets pasted to thin poster board will be fine. The total size is limited to about half the size of a whiteboard in WGR 304. But do pay attention to presentation and organization - don't just put up a slew of 8.5” by 11” sheets taped together. With a class the size it is in 2013, the best bet is to use tri-fold poster boards that stand alone - that way we can use the desks and the boards in the room.
You should use color - it makes a huge difference in crystal structures, band structures, DoS plots etc.
Why a poster as well as a paper? It's so that you can share your work with the other students and learn something from them, too. Science is about communicating ideas and results, so you need to practice that. So come up with something interesting to tell your peers.
Pitfalls: Don't write a technical manual (“go to this menu, and click this button”). Don’t consider the PH575 instructor as a target reader (in the sense that she knows what you have been taught). Matt or the grader may well give the paper to a faculty colleague or a senior grad student as a check to see whether that person thinks the paper is well constructed.
Q. What is a CIF file?
A. The Crystallographic Information File (CIF) is the standard for crystallographic data exchange prescribed by the International Union of Crystallography. It was described in a paper in Acta Cryst. (1991). A47, 655–685 by S. R. Hall, F. H. Allen and I. D. Brown. Here is some of the text from a CIF file describing anatase TiO2:
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Ti1 Ti+4 0 0 0 1 0.0
O1 O-2 0.2821 0.2821 0 1 0.0
Translating the above code into english: “There is a Ti atom at (x,y,z) = (0,0,0) and an O atom at (0.2821a, 0.2821b, 0), where a and b are unit cell dimensions."
IMPORTANT: Please load the CIF file firstin Quatum Vesta(to see the crystal structure), then resave, and then re-load the CIF in BURAI for DFT calculations. BURAI often mis-intrepret web-base CIF unless re-saved in VESTA first.
Q. How do I know my band structure is right?
A. Look in the literature - someone else is bound to have calculated it. Results will vary a bit with different methods used. Remember to reference others' work in your report.
Q. My material has 80 atoms per unit cell - that OK?
A. 80 atoms is too big for our system.
Q. Can I study doping, (eg B-doped Si) or solid solutions like ZnS_(1-y)Se_y?
A. No, it's best to stay away from these because you will need a much larger unit cell. This is because if you replace say 1% of Si with P, you will need 100 unit cells (99 with Si and 1 with P) to define the basic unit. Refer to the question above.
Q. Can I study graphene?
A. We've looked at this material in class, so if you really want to do this, look for a new, related 2D material or try some advanced options.
Q. Can I study conductivity as a function of temperature?
A. No. All calculations are inherently T=0 calculations. There are no excitations of the system included.
Authored By Janet Tate, modified by MW Graham