<div dir="ltr"><div><div><div><div><div>Dear Sir,<br></div><br></div>you are right. Experimental band gap for my compound is 2.0eV. The maximum band gap on increasing U value for my calculation is 1.117eV at 10 eV. So, should I increase U value beyond 10eV ? Untill now from my literature review, the value of U is less than 10 eV. <br>
</div>Secondly, if suppose a compound has not been studied experimentally then how we choose calue of U ?<br><br></div>Thank you<br></div>Zaid<br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Jul 20, 2013 at 1:48 PM, <span dir="ltr"><<a href="mailto:tran@theochem.tuwien.ac.at" target="_blank">tran@theochem.tuwien.ac.at</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
I have never heard that the proper value of U is the one when the band gap<br>
starts to decrease. Usually the value of U is chosen such that the<br>
calculated properties (e.g., band gap or magnetic moment) agree with<br>
experiment.<br>
<br>
F. Tran<br>
<br>
On Sat, 20 Jul 2013, Zaid wrote:<br>
<br>
> Respected Users<br>
><br>
><br>
> I am applying GGA+U technique to considered compounds. In order to select<br>
> proper value of U for specific material, I am changing the value of U from<br>
> 2eV to 10eV with a step of 1eV. I was expecting that on increasing U value<br>
> in the range 2-10eV, a value of U will appear where the corresponding band<br>
> gap will start to decrease instead of increase. That value of U where the<br>
> band gap start to decrease instead of rising will be the proper U value in<br>
> the range 2-10eV.<br>
><br>
> I my case the, every time I am getting increasing band gap values on<br>
> increasing U value from 2-10eV with a step of 1eV. Band gap does not<br>
> decrease in the range 2-10eV. Should I increase the range ? May anyone<br>
> suggest that whether my practice of finding U value is right ? If not how<br>
> can I find proper value of U for specific compound ?<br>
><br>
> Thank you very much<br>
><br>
> Best Regards<br>
> Zaid<br>
><br>
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