<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
<title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
Dear Gerardo,<br>
<br>
It seems that your question need a more general lesson about
theoretical chemistry of physics and does not strictly concern the
Wien2k code.<br>
Let me reorder your questions:<br>
<b>1- Why the Total Energy for my calculated systems it's negative?<br>
</b>In very simple terms, the total energy express the benefit the
system has to be like this (the benefit to be together in such a
bonding and structure).<br>
The total energy express how much the system is stabilized in terms of
kinetic and potential energy ... Thus it is a negative number ... In
other words, lets consider that the energy of vacuum is 0eV, then the
energy of each states defining the system will be negative, and the sum
of these energy correspond to the total energy (which is then also
negative). <br>
Consider the simplest case, an hydrogen atom: the energy of the 1s
orbital is -13.6 eV. So if you have one electron on this orbital the
energy of the system will be -13.6 eV ... <br>
<br>
<b>2- How the Exchange-Correlation term is explained??, i mean, these
terms corresponds to ...?</b><br>
Lets consider a system containing 9 electrons, to deduce its properties
from theory we have to find the wave function and the total energy
defining this system.<br>
It means that we have to solve<b> 1 Schrödinger</b> equation for a
system containing <b>9 interacting electrons</b><br>
<br>
However, the repulsive interaction between electrons cannot be
expressed exactly and we realized an approximation which is contained
in the exchange-correlation potential (the interaction can be
decomposed in two different contribution: exchange and correlation
depending of the spin ...).<br>
<br>
In practice, we do not solve 1 equation for 9 interacting electrons but
we<b> solve 9 equations </b>of non-interacting electrons which feels
the interaction from an<b> effective potential (w</b>hich contain the
exchange-correlation potential at least).<br>
<b><br>
3- About DOS and band structure ...</b><br>
DOS and band structure simply express the distribution of the energy
levels of the system. Because of the solid effect, the states are not
all localized and you have a dispersion of the energy levels forming
bands. These notions are very simply explained in many books and web
sites. I recommend you to search more carefully these notions before
doing any Wien2k calculations. <br>
<br>
Hope this will help you ...<br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
Gerardo Felix Martinez a écrit :
<blockquote
cite="midf91775ad0803042010j45152e9ds43465a2b55a98764@mail.gmail.com"
type="cite">
<div>Hi dear Wien2k users!!! i'm trying to understand as much as
possible how Wien2k works in some specific things, but i can't
understand it fully. That's why i'm asking you for your help answering
this questions:</div>
<div> </div>
<div>- How is the DOS calculated by Wien2k?? I mean, how can this
process be explained in the simplest way possible.</div>
<div>- The same question for the Band Structure.</div>
<div>- How the Exchange-Correlation term is explained??, i
mean, these terms corresponds to ...???</div>
<div>- Why the Total Energy for my calculated systems it's
negative??? </div>
<div> </div>
<div>I hope you can help me.. Thanks a lot in advance.</div>
<pre wrap="">
<hr size="4" width="90%">
_______________________________________________
Wien mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a>
<a class="moz-txt-link-freetext" href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a>
</pre>
</blockquote>
<br>
</body>
</html>