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    Methods to deal with Electron correlations

    Dear all, I am here again with problems:confused: I am now trying to get some feeling of electron correlations in solid, following some literature, but it seems like that ALL confusing things lie here---there are s o many methods, and usually different people insist on their own one...
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    Question on Virtual Crystal Approx.(VCA)

    Dear all, I am now intended to do some first-principle calculations on disordered system, where VCA is an effective method. However, as to practical implementation using different methods, say Plane-Wave Pseudopotential, FPLMTO, FPLAPW, it's a litter hard to get a clear picture about how to set...
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    Question on how to calculate bond energy in crystal.

    Dear all: Since bond energies in crystal are very important in say single crystal growth theory, and it seems very difficult to do such calculations. However, can someone give me some hints on this task, or if there is a perfect solution, please let me know. Sincerely Hongbin Zhang
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    On strongly Correlated System

    Ohh, it's an exciting paper while makes me frustrated. One can interpret 'the complex system' intuitively, however, how can we describe it mathematically? Using Hubbard mode or t-J mode? Or even chaos theory?
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    On strongly Correlated System

    Thank you very much, dear Zapperz. And May you a good journey.
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    On strongly Correlated System

    I am no familiar with this area, and I want to know whether can we say that materials including atoms with d electrons are strongly correltated sysytem?
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    Wht abt molecular arbital?

    I have been thinking on this question during the last few monthes on my spare time. I think molecular orbitals, such as HOMO, LUMO, are the same as those of an atom, if we can consider molecular as a pseudo atom, since there are s, p, d orbitals in atoms. However, the origin of molecular...
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    How to solve Eliashberg Equations?

    Thank you for your reply,dear Zz. I also want to solve them by myself, but it seems to be an impossible task for me. So would you to give me some hints, clues or general method about how to solve this kind of equations? Or would you refer me to somebody who has done these work?
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    How to solve Eliashberg Equations?

    Dear all: Now I am try to interpret superconductivity in MgB2, its transition temperature can be get by solving Eliashberg Equations. However, I cann't find any porgram which can do this job, so can someone give me some links or package refer to solving Eliashberg Equations? Thank you...
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    Question on superconductivity theory beyond BCS.

    Thank you very much, dear Zapper. About McMillan's theory, would you be kind to make a short comment?
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    Question on superconductivity theory beyond BCS.

    from cond-mat/0106143 "Eliashberg theory goes beyond BCS theory because it includes retardation effects; however, it is still a weak coupling theory, in the sense that the Fermi energy is the dominant energy, and the quasiparticle picture remains intact." Here I am confused. From the authors...
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    Question on superconductivity theory beyond BCS.

    Dear Zapper: Yeah, I have read the two papers and those related, and what I want to do is to get an understanding of superconductivity dominated by eletron-phonon interaction following their papers taking MgB2 as an example. And though BCS is important to tell us superconducting mechanism, i...
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    Question on superconductivity theory beyond BCS.

    Dear all: Now I am trying hard to interpret superconductivity in MgB2, and when reading some paper such as J.Kortus et. al, J.M.An et. al on PRL/PRB, I find that their way to weigh transition temperature is different, for instance, in J.Kortus's paper(PRL86,4656(2001)), they use...
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    Q:How to interpret band structure?

    Dear all: I've been tortrued by this problem for a long time, plz help me as possible as you can. 1. I want to know, after one get a dispersion picture of E(k), how to judge one of those curves stems from, say, px/py/pz sigma/pi (bond?)? That is to say, how to judge the curve's charater...
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    On projected Density of States

    Thank you for your reply, marlon. Yeah I am reading the paper by R. S. Mulliken, however, what I really do is calculation with plane-wave pseudopotential ab initio method and I want to interpret my results. Thus I wonder how can one derive the same meaning for plane waves as AOs in Mulliken's...
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    On projected Density of States

    Dear all: I am frustrated in the concept of the PDOS, may someone be kind to refer me to the origin of this concept? Thanks. Regards
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    Help: How to interpret energy band?

    I have fixed it. Thanks very much So lazy to ask a so easy question, and now I have fixed it. I use PWSCF to do some calculation and now I have two powerful softs: XCrySDen and PWgui. With them,I find it easy to try again and again until you get a correct data. Thanks everyone...
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    Help: How to interpret energy band?

    Sorry for bringing inconvenience to everyone but I really want it to be a new post... Anyway, hope your help sincerely and I will follow the rule next time.
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    Help: How to interpret energy band?

    HELP: how to build unit cell? Shame that there are so many things I don't understand~~~~Here is my another question. Since dear ZapperZ and Gokul43201 have told me what basically a energy band mean, and I have read some. However, when I want to calculate band structure of some simple...
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    Help: How to interpret energy band?

    Thanks very much :!!)
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    Help: How to interpret energy band?

    Thank you very much again!~~~~~~~ As to the symmetry of crystal and the first Briillouin zones, I think I have got some knowledge of them. And what have tortured me for so long a time is how to assign one of the curves to, for example, sigma of B-B. And from the energy band what exactly we...
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    Help: How to interpret energy band?

    As we all known, energy band is very important to everyone who want to go longer in physics, especially in condensed matter physics. However, as a student of physics, I am shamed to say that I cannot interpret the picture of energy bands well, thus would someone be kind to tell me the secret or...
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    Question on BCS Theory

    Here I list my interpretation and may you be kind to tell me they are right or wrong: Ground State of superconductivity--all electrons are in cooper pair states, which let the total energy be lower with respect to "free electrons"-which distribute in Fermi-Dirac method. However,here I get a...
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    Question on BCS Theory

    Thank you very much! However, I don't think there's the book in our library thus I want to buy it. Then comes the problem: Maybe there are two edition of the very book which were published in 1975 and 1996, respectively, which one should I get? And is the title of the book exactly...
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    Non Linear optical Coefficient

    thank you, dear Mike H thank you very much for your guideness, and information you told me. However I am not exactly the one who is definitely to do calculations on non linear optical coefficient-my subject is superconductivity and I want to try to do some exercise ( or may be do some research...
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    Question on BCS Theory

    Hello Everyone here: I am reading the very paper of BCS theory by J.Bardeen, L.N.Cooper and J.R.Schrieffer (Phys.Rev.108, 1175,1957). But I find so many things hard to understand for me, though I have finished my Quantum Mechanics and Solid State Theory, especially a paragraph list below...
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    Non Linear optical Coefficient

    sorry for my unclearness, and thanks for your kind reply. Here I want to make it more clear: what I want to know is that how one can get 2-order or 3-order non-linear optical coefficient(is this need definition?) of an organic molecular through calculation result by GAUSSIAN98/03?-because I...
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    Non Linear optical Coefficient

    hoho Isn't anyone here? 555555555555
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    Non Linear optical Coefficient

    :confused: Hello everyone: I am a newbie in Quantum Chemistry and I want to do some calculation on some physical properties such as the title shows. However, as we know, lots of package can't give you exactly what you want,you have to tackle with some succeeding process to get a beatiful...
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    Sorce theory? What is it?

    It must be very interesting! May somebody e-mail the book about it to me? thanks my email is:leoant21@hotmail.com leoant
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