[CP2K-user] [CP2K:11308] Re: energy fluctuation in GEO-OPT

Marcella Iannuzzi marci... at gmail.com
Thu Feb 21 08:19:37 UTC 2019

Before getting involved in AIMD simulations, probably you need to go back 
to books to learn about condensed matter electronic structure theory. 
Can your reproduce the electronic properties of this MOF with your DFT 
Anyway, to simulate an isolated fragment you need a CELL that is about 
twice as large as the system and you have to choose a proper Poisson 

On Thursday, February 21, 2019 at 2:52:47 AM UTC+1, M. Memol wrote:
> Thank you so much for your response. Actually I am an Abinitio user and I 
> am very new in AIMD. And the part MD is a kind of black box for me. But 
> before doing AIMD, and along with studying precious book of prof. Hutter, i 
> decided to get familliar to the program package with the aid of the 
> excerices. Yes this an isolated part of a crystal. A first building block 
> of a MOF. Before your answer, I did some modification in the input. For 
> example i turned on the periodic option and as a result, the menrioned 
> fluctuation disappeared and scf coverged. But what if I do not want to use 
> periodic system and just optimize this isolated part?
> On Feb 20, 2019 6:19 PM, "Marcella Iannuzzi" <marc... at gmail.com 
> <javascript:>> wrote:
>> Either the structure or the DFT setting must have serious problems, since 
>> the SCF is never converging. 
>> For example in SUBSYS you use "periodic none" with a box of 15 Å, but 
>> your system seems to be larger than that.
>> On the other hand, POISSON is still using PBC.  What do you want to 
>> model, an isolated subsystem of a crystal?
>> With such a wrong electronic structure you cannot expect any meaningful 
>> evaluation of the forces.
>> Before starting the GEO_OPT you need to be able to get a reasonable 
>> electronic structure of the initial state.
>> Regards
>> Marcella
>> On Wednesday, February 20, 2019 at 6:16:39 AM UTC+1, M. Memol wrote:
>>> I am a very recent user of cp2k and I am really sorry if my question is 
>>> a naive one. I am getting familiar with calculation by cp2k. I am doing an 
>>> geometry optimization run on a MOF building block. But comparing to the 
>>> examples, the energy fluctuates. input and output are given below. any 
>>> comment?
>>> thanks in advance 
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