Density Functional Theory example essay topic

Physicist Walter Kohn was born in Vienna, Austria, on March 9, 1923, into a middle class family. Kohn's family owned an art shop when he was a child, and they remained successful with the business until Hitler came to power. For five years before the rise of Hitler, Kohn attended the Akademische Gymnasium, which was an extremely reputable school. When Hitler came to power, he annexed Austria, and forced Kohn and his family to move from the home.

They made for England. Upon arrival, Kohn had decided that he wanted to become a farmer. This was because he had seen too many unemployed intellectuals during the depression. However, he caught meningitis, and became to weak to follow a career in farming, so turned to science. In May, 1940 Winston Churchill ordered all persons with enemy passports to be deports to internment camps in Canada, and since Kohn was from Austria, he was deported. After exiting these camps, he attended The University of Toronto.

He later graduated from The University of Toronto with degrees in mathematics and physics. A year later he went back, and emerged with a degree in applied mathematics. From here he began to work in the United States, which eventually led him to be accepted into a fellowship, and attend Harvard University. He graduated from Harvard with a Ph. D. in Physics.

Kohn is a man of many skills as well, as he currently holds the job of Professor of Physics, Emeritus and Research at the University of California at Santa Barbara. Professor Kohn has also received honorary doctorate degrees from nine universities worldwide. The list of degrees awarded to this extraordinary physicist show us just how renowned he is in his field of study, and just how important the contributions that he has made are. Density Functional Theory When Quantum Mechanics were being developed during the time period from the 1920's to the 1950's, theoretical physicists realized that it is not possible to calculate the exact mass and location of an electron at any given time. To exactly describe an electron or photon, you would use the probability wave functions, called "psi" functions and developed by Heisenberg, which were extremely complex. These functions describe individual electrons as clouds of probability.

This made the process of accurately describing the characteristics of a chunk of something nearly impossible. When Professor Kohn was a student at the University of Toronto, after being released from the internment camp for Germans, his professors encouraged him to work on physics. The three separate bodies scattering problems which he worked on in math gave him a conceptual basis for the prediction of describing the average density of electrons in materials was about as accurate a way to describe them as using the aforementioned probability clouds. The Density Functional Theory is the name of the process Kohn created for describing the average density of electrons in materials. The wave function "psi" of an N-electron system, mentioned above as the method for calculation which Professor Kohn replaced, includes 3 "N" variables, while the density, no matter how large the system is, has only three variables "x", "y", and "z". Moving from E [psi] to E [n] in computational chemistry significantly reduces the effort needed to understand electronic properties of atoms, molecules, and solids.

Computation along this line provides the possibility of the linear scaling algorithm currently in use, whose computational complexity goes like O (Nlo gN), essentially linear in N when N is very large. The other advantage of DFT is that it provides some chemically important concepts, such as elctronegativity (chemical potential), hardness (softness), Fukui function, response function, and so forth. These concepts can be conveniently used to explain chemical properties of molecules. (Walter Kohn Winner of the 1998 Nobel Prize, 2000) Aside from the DFT, Kohn contributed to many sub fields of Physics. In 1949, for example, he worked for the polaroid lab. This was to explain mathematically how charged particles falling on a photographic plate create an image.

In 1950 through 1952, Kohn worker with Niels Bohr and Wolfgang Pauli on the so called "inverse scattering problem:" when a particle is scattered by an electric potential, what information can be gathered from the process? His summer job work at Belle labs in 1953 led to the thirteen years studying energy thresholds for displacement of nuclei in semiconductors and transistors. His study of quantum particles included showing, in 1966, that superconductivity occurs even in purely repulsive interactions, contrary to conventional thought at that time. However, Kohn's greatest accomplishment took place in the 1960's, when he hypothesized that the density of an object enables you to determine all properties of that object. The Density Functional Theory 7 "Walter Kohn Autobiography". Nobel e-Museum. (c) 2002.

Viewed 2.13. 03 "Density Functional Theory". Ohio State University. (c) 2002. Viewed 2.13. 03 "Walter Kohn Winner of the 1998 Nobel Prize".

Ona Wu. (c) 2000. Viewed 2.13. 03 "Home Page of Density Functional Theory". University of North Carolina. (c) 2003.

Viewed 2.13. 03 " web". No Author Given. (c) 2001 Viewed 2.13. 03.