So we recently had a ‘blizzard’ here where I am, and while my area didnt get iced, we did get beautiful lovely snow. As a budding crystallographer, I looked at the snowflakes, really big crystals and went, “OMG! Tropochemical twinning! Merohedral twinning! SQUEE SQUEE!” After realizing my inherent nerdyness, I stumbled upon to this website from Caltech talking about the crystallography, physics and chemistry of snowflakes. Utterly and completely fascinating. Everyone should check it out. I’ve been lucky enough to see a 12 sided snowflake. Even the three sided ones. I really dont think these are ‘crystals’ but probably more like quasicrystals that have the ‘forbidden’ 5, 7, 9 and 12 symmetry. Or it could just be twinned up the wazoo. Either way, it’s really interesting. Go read!
Archive for December, 2008
So I wasnt planning on putting this down, as it has NOTHING to do with chemistry, but there’s this DJ Masa from South America who mixes up Jpop/Kpop and USpop. I’m a huge pop junkie, really and well, this will probably destroy any chemistry cred I’m trying to build, but oh well. This stuff is just cool.
Wondergirls is a Korean pop girl group that has a song called Nobody. Amy Winehouse is awesome, and he’s using the background of Back to Black. It works perfectly here.
This one is more pop mixed as it has Britney Spears, Ivy (another Asian girlgroup), Tsai, and another who I forget her name at the moment. Either way. It’s pretty cool.
His website is: here.
So, now that you’ve survived freshman and sophomore year and you’re still a chemistry major, congratulations! Junior year is when things really suck…
6) Junior Year
This is a difficult year. Physical chemistry, inorganic chemistry, analytical chemistry, biochemistry, (insert chemistry elective here). Back in undergrad, we needed two semesters of all these classes, so we usually distributed this amongst junior and senior year, especially since the labs that came with them were especially difficult.
If your school offers a technical writing class. TAKE it. Writing lab reports is not sufficient in learning how to write technically.
Pay attention to your classes. This is very important stuff as it’s general chemistry come back to haunt you in a more difficult and indepth form. I really liked pchem, inorganic and I was meh about analytical. Biochem was fun though, it was okay.
At this point, you should be in a research group, if you want to go to graduate schools. Hopefully you have REU experience underneath your belt as well, so just keep up the studying. Try to go to an ACS meeting and present some of the research you’ve done before. It’s a fun experience and always looks good on grad school apps. If your school has the Beckman Scholars program, apply for it. It’s competitive but it’s really good as well. If you’re an organiker, try to go for the Pfizer Undergrad Scholar program as well. Apply for undergrad research fellowships at your institution as they can go to travel as well. Also, apply for a Goldwater if you want. It’s a hella prestigious scholarship, and people who win these often go on to win NSFs, Hertzes, etc.
The summer of your junior year, if you’re interested in graduate school, start making your list. Start studying for the Chem GREs. If you’re apping for the NSF your senior year, make sure you get the waiver so the NSF can pay for your GREs instead.
7) Senior Year
Ahhh, senior year! You’re almost done. Some people go supersenior year as well, but the same advice applies. Hopefully, you’ve made your list of graduate schools. Put them into three categories: Wishlist, Reasonable, and Safety. Have most of your schools be in the Reasonable category and you’ll be fine. If you are applying, make sure that you ask your letter recommenders early. Since most grad school apps are due in December, start asking your letter recommenders in August/September.
Dont get senioritis! Finish off your classes but have fun as well, it’s your last year to really take a spring break, as there is no spring break in grad school and the real world. Treasure your friends, and dont slack off. You can slack off in the summer after graduation!
This year, make sure you apply for fellowships. As my advisors (both in undergrad and in grad school said), you definitely wont win any fellowships if you dont apply. It’s a good exercise to write the proposals even though very few people win in chemistry. It’s tough out there, and it’s good practice for future scientific writing.
Well, with all that said and done, you’ve hopefully graduated with your chem degree. Congratulations, you are a chemist! As I’m only a grad student, I dont feel that comfortable putting stuff down for grad school..perhaps when I graduate I’ll do it. But once you graduate with your B.S. or B.A. you’re a chemist! Congratulations!
So I decided to write some more since no one is in lab and I have reactions setup, so time to blog I guess.
4) Freshman year
So at this point, you still want to be a chemist, after going through everything you have back in high school. Good for you! I highly recommend taking intro chem at your respective college, because AP Chemistry leaves a lot to be desired. Mainly the intro lab techniques (titration, gravimetry, etc) are very important and build a solid foundation. I dont care what school you went to, but going straight into organic chemistry is not a good idea, simply because of the lab component you’re missing. I’ve taught people who didnt take freshman chem lab, and oye, their technique later on is SEVERELY lacking.
If you’ve declared a chemistry major, take the intro chem for chemistry majors. This is always an intensive course,and way more than anything taught at the AP level. It builds solid foundations and will help you out for the rest of your college career as a chemist. Back in undergrad, I took intro chem for the chem majors, which was crosslisted as ‘honors’ chem, and it was tough. Our exams were a lot more in depth and we covered topics at a more in depth level, to when pchem came, it was a synch.
I also TAed an intensive intro chem class here as a grad student, and it’s well worth it. The topics they cover are very advanced and the students learned more than their regular intro chem counterparts.
If you can, start looking and reading various research descriptions in your department. A lot will still be over your head, but if you impress your chem prof, he/she might offer you a research position. I got one straight off the bat my freshman year, so I was very lucky in that sense. But dedication is always good and you should try for it.
Another note: APPLY for REUs. I applied for them starting my freshman year, and was also very lucky to get one, but this research experience is always paid for and you get to travel, and it’s always good if you’re applying for grad school later on. Make sure you apply to many of them, because as a freshman, you’ll be extremely lucky to get into a program right off the bat.
What classes to take freshman year? Intro chem, calculus, physics (and if you want intro bio). Take the physics for physics majors (if they have that option), and at a minimum take physics with calculus. This will be really good preparation for physical chemistry later on.
5) Sophomore year
Now sophomore year. You’re taking organic chemistry in the minimum, and well, I hated organic, but it’s a good skills to have, especially since the chem GRE is basically 90% organic later on. Some colleges just have calculus, but you want to take as much math as you can. I was a physics major in undergrad as well, so I had a bajillion math classes, but in the minimum, to prepare you for the rigors of physical chemistry, you want partial differential equations, vector calculus, and linear algebra/matrices (so that’s three classes beyond your usual calc 1 and 2 requirement). These will be very important in quantum chem. Eigenvalues, eigenvectors, all that, very good for pchem.
At this point, if you didnt get a research position, you will want to get one. Talk to professors. Email them (but not in an obnoxious spammy way) and attend seminars. These will be over your head, but your enthusiasm will be duly noted by your professors.
Also, dont be annoying to your grad TAs. I had several freshmen/sophomores who wanted to do research in my lab group. There were ones I wanted, there were ones who just solicited their services. It really depends on your TA as to what approach they like. I prefer doing the whole: “So, I’m looking for an undergrad lackey” invitation to the students in my classes who are good. Some will just accept unsolicited offers, but oh well.
Again, APPLY to REUs. So, I’ll write an entry about REUs and successful applications later on. I was extremely lucky in that I got into an REU every summer, so I think I have how to apply for those down pat.
So I remember reading the “So you want to be a physicist” back in the days that I did want to be a physicist. I still do, to an extent, but solid state sciences have become quite interdisciplinary with chemistry and physics, hence I’m studying both. I digress.
I’ve looked around and havent been able to find any entries or anything of the like with chemistry, and since my adorable little niece told me the other day, she wants to be a chemist like me (awwww, isnt that cute?), I figured I’d right up a piece. So Jessica, this goes to you my dear little niece.
So You Want To Be a Chemist, Part 1: Elementary, middle and high school
My niece is only six, so I’m starting early. We have to train her afterall, and any other young budding chemists out there. I know from experience, cause well, my parents are both involved in the chemical sciences, so I think that’s why I probably ended up where I am.
So you /think/ you want to be a chemist! That’s really cute at the elementary school age, and so at this point, the parentals should be exposing all young children to the wonders that is science. Physics, chemistry and biology and even engineering should be taken in, and there are wonderful shows out there that kids can watch on PBS. Back in the day, I had Mr. Wizard and 3-2-1 contact, but alas, those are gone. I dont know what the current shows are, but I still highly recommend the Discovery channel for some good parent-children TV watching. My favorites are still especially Shark Week, Dinosaur Week and any good astrophysics stuff.
Back when I was a kid, Nova on PBS was a delightful source of edu-tainment. Parents, if you’re not involved in the sciences, you can learn a lot from these shows as well, as they arent specifically made for us geeks. In fact, they’re made to reach out to the masses to get a growing interest in the sciences, so make sure your children watch, I know I make Jessica and my own siblings watch. Ha!
At the elementary and middle school ages, museums are always a wonderful option. Start off with children’s museums that show the wonders of science. There are always demos, lots of games children can play, and of course, the demos.
There are lots of books out there that show neat little demos and tricks that can be made with science. Right now, for instance, there is a book called “Inexpensive Experiments for Young Children”. Back when I did demos for young kids as an undergrad, we used a lot of tricks in that book and a series of other books that were simply fun and awesome.
Here’s one that kids generally like, and it’s easy to do.
“Make your own GAK”
Ingredients: Disposable cups, Elmer’s glue, food coloring, and Borax (you can get this in the dishwashing aisle of your grocery store)
Procedure: In a disposable paper cup, pour in Elmer’s glue and food coloring. Mix well with a toothpic until desired color is achieved. For extra coolness, simply swirl different colors in with a toothpic for a tie-dye effect. Meanwhile, prepare a supersaturated solution of Borax and cold water. (Take a cup of borax and mix it in half a gallon of water). Once the Borax is nice and dissolved, mix the solution in with the Elmer’s glue mix. Polymerization and crosslinking will occur to produce ‘gak’, and have your little one mix with his/her little hands in the disposable cup. The glue wont stick to the little one’s fingers and will instead continue the polymerization process. Decant the excess Borax solution and play with your gak!
(Parents, it’s easy clean up if you get it on the carpet. Use soapy water to clean off and use a little Borax solution to make sure there wasnt any glue in there. Then vacuum).
See! That’s one of the experiments we did with ACS. All the little kids loved it. Speaking of ACS, if you’re a parent who has a budding little chemist, bring them out to local OPEN HOUSES in different universities. My undergrad alma mater always had an open house for the locals where all the student organizations would have booths and generally try to get kids to go to college and encourage their parents to start saving up for it.
With ACS, we always did the GAK experiments and made liquid nitrogen icecream. It was a treat for everyone, and the kids became excited. The SPS (Societyof Physics Students) collaborated with us, and we showed the YBCO and BSCO superconductors as well, so it was fun for all the student affiliates and the families.
2) Middle School
So all that stuff is good for elementary school, but what about middle school? My own siblings are in that age, and this is what we do to encourage their inner geekyness. Science fairs! Oh, yes there’s science fairs starting at kinder, but at the middle school level, you can start doing neater stuff.
We’re not talking about high level experiments, but simplethings can and should be done to promote your budding chemist’s interests and experimental skills. At this stage in the game, just general training in critical thinking and analytical skills and the introduction to the scientific method should still be used. That way, your budding scientist can go off to be an engineer, or a biologist, chemist, geologist, physicist or mathematician.
Take your Pre-AP courses. Challenge yourself. Take Prealgebra in 7th grade, and Algebra in 8th. If you’re really good at math, take it early, and definitely go for the TIP (Talent Identification Program) at your local school. This is essentially taking the SAT in the 7th grade to see if you qualify for some special summer programs at Duke, Stanford, John Hopkins, Northwestern, and a fine variety of other schools. If you manage to get into the program, take a science or math related course and inundate yourself in a pre-college experience by staying at the dorm and actually learning in the summer. I know these programs continue after the 7th grade, so if you can afford it, go for it. Scholarships based on need are offered, so dont feel like this is a program only for the rich. Here’s the DUKE TIP website. Apparently, they have a 4th-5th grade program now starting in 2009! http://www.tip.duke.edu/
3) High School
So, you’ve done what you can in elementary and middle school. High school is where you can actually start being a real scientist in training, if you feel that’s your passion. That’s when I started anyway. Make sure you take advantage of the Pre-AP and AP Curriculum at this level. This curriculum is always good. Pre-AP Biology, Chemistry, and Physics are good, and if you can, double up with some AP Biology, AP Chemistry and AP Physics. Back at my high school, I was able to take AP Physics and AP Biology my senior year, and I took AP Chemistry with Pre-AP Physics my junior year. It was a sweet deal. Of course, make sure you take AP Calculus AB and AP Calculus BC if your school offers it. Take advantage of what you can.
If your school doesnt have extensive AP curriculum, look into a dual credit program. Local community colleges often partner up with high schoolers so that you can take classes (usually for free) at a local community college. If you’re going to a public school for college (like I did), these classes typically transfer. Even if you dont, they’re a good foundation that you can use to further your learning once you are in college. In addition, look at the different curriula your school has to offer. We had a minimum, regular and distinguished plan. The distinguished plan required AP tests (minimum score of 4), and you needed 3 of them. In addition, we had the independent study option where you could find a mentor to work under (some people interned in journalism, while I and a couple of my friends went to the local colleges to do research. I did it for the experience, not to try to get a SIEMENS Westinghouse Competition. That’s what other programs are for ^_^). It’s a good experience, so if your school has it, look into it.
Science fairs are your friend. Science fairs are also where people start differentiating themselves. I noticed that those kids with parents in academia, engineering or generally had money, sent their kids off to various professors at nearby colleges to do their science fair projects. As one of the kids who didnt do that, I HATED those kids, but if you can go for it try. Most professors dont hire high schoolers, and in all honesty, as a high schooler, you’ll be doing the really simple stuff, but it’s good training anyway. Back in undergrad, we had one of those high schoolers who wanted to go for the SIEMENS Westinghouse Competition, and I was his undergrad mentor. He helped me on my project and he got to do a presentation on it.
My experience with my high schooler was not a good one. He wanted to do it for the money. HE wasnt passionate about the science and I’m pretty sure his overbearing parents made him do it. Do not be one of these kids. Your mentor will only get angry and frustrated. Trust me, we can tell if you’re doing it for the wrong reason.
HOWEVER, if you are passionate, there are some programs that are good to try. In Texas, I was part of the Welch Summer High School Scholars program. These are all the kids who wanted to do experiments and learn. We were all passionate and we all ended up SIEMENS Westinghouse types and went on to International Science Fairs at some point. This was a fun experience, but generally, other states have programs like these as well. There’s one program at MIT that accepts high schoolers from all over and is quite competitive. It’s an international program, so really only the top of the top get in, but I’ll look up the information and post it at a later date.
If you really want to be a chemist, I’d do these types of programs. But remember, do it because you want to, not because anyone else wants you to. If you do it for the wrong reasons, you might get burned out at a young age and then not want to join a STEM field later on. I’ve seen it happen to friends of mine and it’s a waste of potential, IMHO, as they ended up being business majors who make way more money than me now…(waittaminute)
Well that’s all for part 1. Later on, I’ll do pt 2. College.
Tarun K. Bera 1, Jung-Hwan Song, Dr. 2, Arthur J. Freeman, Prof. 2, Joon I. Jang, Dr. 2, John B. Ketterson, Prof. 2, Mercouri G. Kanatzidis, Prof. Dr. 1 * Angewandte Chemie Int. Ed. 41, 7828 (2008)
So this stuff is really cool, at least I think so anyway. This comes from the Kanatzidis, Ketterson and Freeman groups at Northwestern University. So, what did they make exactly? Bera et al. synthesized two new semiconducting chalcogenides, LiAsS2 and NaAsS2, that has the strongest nonlinear optical response. The previous record was held by a silver compound, but these materials has at least ten times stronger response than that!
Oh noes, it has Arsenic! Big deal. It’s in a 3+ oxidation state, but the other pnictides, particularly Sb and Bi and P all in 3+ states are just as toxic as arsenic. That’s one of the problems with chemistry is that it gets a bad rap, but I digress, back to the awesomeness of this paper.
So what is needed for a good NLO material. There’s a paper from the Poeppelmeier group also at Northwestern University (first author P. Shiv Halasyamani, look it up, I’m too lazy to find the link and put it here) that talks about what is needed for good nonlinear optic materials. Mainly, it requires a noncentrosymmetric space group.
Now, NaAsS2, I looked it up in the Find It database and Pearson’s crystal database typically crystallizes in a centrosymmetric space group. Basically, that sucks and wont get any NLO response. Using a polychalcogenide flux, a new form of this material was synthesized by the Kanatzidis group crystallizing in a NONcentrosymmetric space group.
This is good, but another thing that is needed for a strong NLO response is polarizability of the atoms. If you look at the crystal structure presented in the paper, arsenic forms tetrahedral chains with sulfur that are really big electron cloud wise and hence has a strong polarizability. But let’s use different atoms instead and we too can get an Angewandte Paper!
Bzzt! Wrong! Phosphorous (the element above arsenic) is simply too small and will NOT produce tetrahedral chains that are noncentrosymmetric (again I looked this up). Antimony (the element below arsenic) is simply too big, and will provide a large coordination sphere for sulfur to go around. So really, you’ve optimized the tetrahedral geometry of the arsenic-sulfur units.
Now, this paper, I think is extra sooper awesome because it combines solid state chemistry, with solid state physics. These two things go hand in hand, and the Freeman group (one of the Gods of electronic structure calculation) used full potential linearized augmented plane wave (FLAPW) method for the calculations.
What the heck does that mean? Well, it’s simple really. For the atoms in the crystal lattice, they use plane wave equations of the form psi = e^(ikx) and take into account the full potential of the electrons for each atom. What happens in the interstitial spaces? Well for that they assume that the electron acts as a ‘free electron’ as if it’s in a free electron gas, so your psi = Asin(x) + Bcos(y) equation from your elemental quantum class should fit. It’s a really neat technique, and the added awesomeness is that for the exchange correlation term in the Kohn-Sham equation that they use is using screen-exchange localized density approximation (sx-LDA).
sx-LDA simply uses a local density approximation for your electrons (it’s a good DFT method), but is better at calculating bandgaps for compounds due to the Lagrange parameters in the equations actually having more physical meaning. This is a gross oversimplification, but let’s move on.
So, what is the take home message, after getting through the nitty gritty. Arsenic is awesome. It’s the perfect size to form large enough tetrahedral units to be quite polarizable and have the noncentrosymmetry required to make a good NLO material. These materials have the strongest second-harmonic generation response, beating out the previous standard, and can be synthesized in a facile manner using a polychalcogenide flux method.
what is polychalcogenide flux method? I think I’ll separate that in another entry. But I still have stacks of papers to read so I’ll do that later.
So I put up that earlier post showing the Fourier transforms. For those of you who do know the answer, congratulations. You know the basics of symmetry! Crystals are said to be periodic. As such, they fill all space and have translational symmetry. 2, 3, 4 and 6 fold symmetry shows translation. If you look in the earlier post, then you’ll see that the pictures to the left have translational symmetry in the atoms, while the 5, 7, and 9 fold do not.
5, 7, and 9 fold symmetry does exist however, in the forms of quasi crystals. These are materials that are ordered, but nonperiodic in the short range, but have a long range order. They tend to produce X-ray diffraction patterns that are penrose tiles and all sorts of cool stuff. Quasicrystals can be solved by traditional X-ray crystallography, but for that you need to go into higher dimensional crystallography. That is another topic all together. And for now I’m tired so that’s where I’ll end. Huzzah!