There is a tutorial at the Opium pseudopotential generation project, see
link below. Although you might not want to take the time to fiddle with the
software, the tutorial does a good job explaining the different
modifications that can be made to norm-conserving pseudopotentials.
http://opium.sourceforge.net/
Scott Beckman
Assistant Professor
Department of Material Science and Engineering
Iowa State University
sbeck...@iastate.edu
On 7/13/09 2:57 PM, Hui Tang hui.t...@yale.edu wrote:
When we build a pseudopotential (psp), we froze the inner core states and
treat only the valence electrons due to the fact that the properties of
materials are largely determined by the outer-layer valence electrons. In
order to obtain a psp with good transferability, there should be very small
overlap between core and valence electron distributions which is true for most
light elements. For most the elements, the overlap between core and valence
electron can be so large that the psp built in the usual way cannot lead to
the correct properties of materials composed of that element (e.g., Na, K).
There are two methods to solve the above problem. 1) Nonlinear core
correction, we use an artificial core charge distribution to replace the real
core charge distribution. When building psp, we substract the contribution to
Vxc and VHartree, which comes from the artificial core, and when using the
psp, add the corresponding ones (see PRB 26, 1378). When doing nonlinear core
correction, we don't increase the number of valence electrons but only
increase the cutoff energy for plane-wave calculations due to the added core.
2) Semicore states, which means including some states that you usually treat
as core states when you build a pseudopotential. For example, when building a
psp for Ca, we not only include 4s, 4p, 3d but also include 3s, 3p in the
valence states. For this method, we include a lot more electrons (e.g. 8 more
e/atom for Ca), and also need a much large cutoff energy because we have
included much more localized 3s, 3p electrons. So including semicore states
will result in much harder calculations.
In fact, for most cases, nonlinear core correction is already enough for a
good psp and including semicore states is kind of overkill. So my suggestion
is: use the nonlinear core correction when you need it, use semicore states
unless you have to.
Hui
- Original Message -
From: daijianhong001 mailto:daijianhong...@163.com
To: SIESTA-L@listserv.uam.es
Sent: Monday, July 13, 2009 2:42 AM
Subject: [SIESTA-L] semicore state meaning
Dear all,
Some pseudopotential includes semicore state.I wonder what is the meaning of
semicore state and which element includes semicore state?
Best wishes!
Dai
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