From owner-chemistry@ccl.net Thu Dec  4 07:35:01 2014
From: "Herbert Fruchtl herbert.fruchtl[a]st-andrews.ac.uk" <owner-chemistry-*-server.ccl.net>
To: CCL
Subject: CCL: How can I fix the lattice constants derived from the bulk?
Message-Id: <-50791-141204052906-15269-jp64nWZS1c/ro17p/7t/JQ-*-server.ccl.net>
X-Original-From: Herbert Fruchtl <herbert.fruchtl[]st-andrews.ac.uk>
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=windows-1252; format=flowed
Date: Thu, 04 Dec 2014 10:28:40 +0000
MIME-Version: 1.0


Sent to CCL by: Herbert Fruchtl [herbert.fruchtl*o*st-andrews.ac.uk]
If you are asking a software specific question on CCL, you should at least 
mention which software you are using.

Since you are using VASP... You are answering your own question: ISIF=2 freezes 
the lattice constant. You probably also want to freeze the atomic positions of 
the lower layers of your slab.

HTH,

   Herbert

On 03/12/14 01:36, Shawkat Islam sislam/./swin.edu.au wrote:
>
> Sent to CCL by: "Shawkat  Islam" [sislam_-_swin.edu.au]
> Hi CCL users,
>
> I wanted to study surface interaction. So, I optimized my bulk and prepared
> surface based on the optimized bulk. Later I relax my surface with ISIF=2.
>
> How can I fix the lattice constants derived from the bulk?
>
> Thanks
> Shawkat
> sislam##swin.edu.au>
>

-- 
Herbert Fruchtl
Senior Scientific Computing Officer
School of Chemistry, School of Mathematics and Statistics
University of St Andrews
--
The University of St Andrews is a charity registered in Scotland:
No SC013532


From owner-chemistry@ccl.net Thu Dec  4 20:44:01 2014
From: "James Mao xjamesmao+*+gmail.com" <owner-chemistry\a/server.ccl.net>
To: CCL
Subject: CCL: Calculations for excited states
Message-Id: <-50792-141204203954-1945-d4yAQ6mM4ErCG2aUwzOX9g\a/server.ccl.net>
X-Original-From: "James  Mao" <xjamesmao(a)gmail.com>
Date: Thu, 4 Dec 2014 20:39:53 -0500


Sent to CCL by: "James  Mao" [xjamesmao_+_gmail.com]
Dear colleagues,

I am recently trying to carry out calculations to simulate UV spectra of 
relative small molecules (less than 30 atoms). To plot the spectra the 
excitation energy as well as oscillator strength are needed from calculation. I 
noticed that actually there are several candidates which are capable to do 
this. After some practice and comparison it seems to me that it can be done in 
two different levels: TDDFT/CIS(D)/CC2/SOPPA produce quite reasonable and 
similar results, and EOM-CCSD/SAC-CI/CCSD produce similar results at 
next/higher level. My question: in principle, for methods at the same level, is 
any of them expected to produce more accurate data than others? I am not 
talking about the difference of computation cost here since my molecules are 
all small. 
Any comments/suggestion are welcome and will be greatly appreciated.

Best Regards,
James