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Some question about small cluster calculations
Date: 2012/07/27 01:29
Name: sanjeev   <snarooka@yahoo.com>

Dear all user,

I need some information regarding the simulation of small cluster

1- How to optimize the cluster for which triplet is the
ground state or some other state with higher multiplicity
is the ground state.How to achieve this goal with OPENMX.
As for as I know there is no keyword to define the multiplicity
in OPENMX.

2- How to obtain the band structure of the small cluster, because
for this one should require the crystal structure, which is not
available for the cluster. Should I use the cell size generated by OPENMX
as the cell specification in input file.

3- How to obtain the magnetic properties of these cluster. How to define
Hubbard value.

with regards

Sanjeev
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Re: Some question about small cluster calculations ( No.1 )
Date: 2012/08/28 21:15
Name: T.Ozaki

Hi,

> 1- How to optimize the cluster for which triplet is the
> ground state or some other state with higher multiplicity
> is the ground state.How to achieve this goal with OPENMX.
> As for as I know there is no keyword to define the multiplicity
> in OPENMX.

OpenMX does not support calculations with a fixed multiplicity of
total spin moment, but supports a way which determines a magnetic state
during SCF iteration starting from the initial spin configuration.

> 2- How to obtain the band structure of the small cluster, because
> for this one should require the crystal structure, which is not
> available for the cluster. Should I use the cell size generated by OPENMX
> as the cell specification in input file.

For cluster systems, there is no band dispersion, and the energy spectrum is
given by the sum of delta functions.

> 3- How to obtain the magnetic properties of these cluster.

Many papers have already addressed the issue using OpenMX.
Please look those papers.

> How to define Hubbard value.

The Hubbard U used in the DFT+U method of OpenMX is an adjustable parameter
more or less, and OpenMX does not have a functionality to calculate the Hubbard U
based on first-principle methods such as constraint scheme.

Regards,

TO
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