[CP2K-user] [CP2K:17087] Re: Ar Basis sets

[Matthew Graneri]

Hi Marcella,

Sorry for not replying earlier. Your advice really helped. Thank you!

Regards,

Matthew

On Friday, May 13, 2022 at 6:30:02 PM UTC+8 Marcella Iannuzzi wrote:

>
>
> Dear Matthew
>
> I am not a purist of basis set and as long as relevant properties as the 
> representation of the electronic density, the resulting density of states, 
> binding energies are converged (within the level of theory of choice) I am 
> not that concerned in taking specifically optimised basis sets. 
>
> 1) The massive thermostat is a Local thermostat, i.e. it enforces the 
> correct distribution of each component of the momentum
> This means that the velocities of the particles and thus their dynamics 
> are modified, with respect to the microcanonical ensemble, which could 
> potentially lead to thermostat-dependent dynamical artifacts. In general 
> NVE is better for IR spectra
> https://pubs.acs.org/doi/10.1021/ct400109a
>
> Best
> Marcella
>
> On Friday, May 13, 2022 at 6:44:06 AM UTC+2 mhvg... at gmail.com wrote:
>
>> Hi Marcella
>>
>> Thank you so much, I can't believe I missed the UZH Ar basis set! To be 
>> honest, I didn't consider it because I thought that UZH was some 
>> theoretical method I'd never heard of (like HFX or ADMM), and I only just 
>> found out it stood for University of Zurich...
>>
>> Unfortunately, there's no HFX basis set for argon (even on the git 
>> repository), so I can't use that for my system. Would I be right in 
>> assuming that, if I use BASIS_ADMM-UZH basis sets, I should also use 
>> POTENTIAL_UZH and the BASIS_MOLOPT_UZH? Originally, I was going to use the 
>> DZVP-GTH basis sets because (I believe) they are smaller. I also don't know 
>> whether the fact that the UZH sets were optimised against the PBE0 will 
>> cause issues with me using B3LYP as my functional. What do you think?
>>
>> 1) In that case, why would someone equilibrate their system with a 
>> MASSIVE thermostat first, and then again with a GLOBAL thermostat? This is 
>> what is done in the IR spec tutorial...
>> 2) I thought that might be the case. Thank you!
>> 3) Of course, that would make life too easy ;)
>>
>> Thank you so much for your help! I have no experience with any type of 
>> bulk calculation, so your advice is very much appreciated
>>
>> Regards,
>>
>> Matthew
>> On Friday, May 13, 2022 at 1:37:18 AM UTC+8 Marcella Iannuzzi wrote:
>>
>>> Dear Matthew
>>>
>>> There are Ar ADMM basis sets in BASIS_ADMM_UZH in cp2k/data (at least 
>>> present git repository)
>>> The ADMM basis set can be tested against full HFX calculations.
>>>
>>> 1) Using MASSIVE there is one  thermostat attached to each degree of 
>>> freedom, with GLOBAL only one thermostat controls all degrees of freedom
>>> 2) Larger cutoff are needed to collocate on the real space grid 
>>> functions with larger exponents. In this respect, yes there is a basis set 
>>> dependency
>>> 3) No rule to thumb, it depends what the simulation goals are
>>>
>>> Regards
>>> Marcella
>>>
>>>
>>> On Wednesday, May 11, 2022 at 9:15:36 AM UTC+2 mhvg... at gmail.com wrote:
>>>
>>>> Hi there,
>>>>
>>>> I was wondering if I could get some advice/help on running an AIMD 
>>>> calculation to run? I've *no* experience with AIMD, MD, or any plane 
>>>> wave calculations (my only experience is with ab initio methods in ORCA and 
>>>> Gaussian), and no one else in my department has any experience with AIMD 
>>>> calculations, either... I've finally gotten to the stage where I can start 
>>>> an AIMD calculation (it's taken weeks to get to this stage!), but I have 
>>>> come across a persistent issue which I do not have the expertise to solve.
>>>>
>>>> Essentially, I want to simulate my molecular system in a solid argon 
>>>> matrix, and calculate IR spectra to compare with experiment. So far, I've 
>>>> optimised my cutoff/rel_cutoff values, gotten my input files sorted, gotten 
>>>> CP2K installed installed on our local HPC, and tested that it works for a 
>>>> few of the test systems provided for the IR/RAMAN and HFX tutorials.
>>>>
>>>> Based on results from a recent study, I want to use B3LYP with a double 
>>>> zeta basis set, which I am very well aware will take a long time to 
>>>> complete... According to the CP2K website (and my own testing), it looks 
>>>> like using either the ADMM or RI approximations might speed up this 
>>>> calculation to a rate which will be acceptable for our HPC. The problem is 
>>>> that I cannot find any *matching* primary, potential and auxiliary 
>>>> basis sets for argon. In fact, I cannot find any auxiliary basis sets for 
>>>> argon at all.
>>>>
>>>> Is this because argon doesn't require an aux basis set for RI or ADMM? 
>>>> Does anyone know of any basis set families which I could use for my 
>>>> calculations? They'd need to be of at least double zeta quality, and 
>>>> include basis sets for H, C, N, S and Ar.
>>>>
>>>> Also, three unrelated questions (but things which I've been 
>>>> confused/unsure about when trying to learn all this stuff):
>>>>
>>>>    1. what's the difference between the 'global' and 'massive' 
>>>>    thermostats? The academic (yes, there's only one) at my university who has 
>>>>    experience with MD had never seen those terms before, so I'm not sure how 
>>>>    they differ.
>>>>    2. Are the cutoff/rel_cutoff values basis set dependent? As in, if 
>>>>    I swap the basis sets I ran my testing on based on advice I get here, would 
>>>>    I need to rerun my testing for the new basis set, or could I use the values 
>>>>    I determined using the original basis sets?
>>>>    3. Are there any 'rules of thumb' as to how big a cell should be 
>>>>    used for a system like mine? Essentially, I've embedded my molecule in a 
>>>>    crystal of argon. I'm *not* trying to extrapolate this to a larger 
>>>>    crystal structure (I think that means it's 'non periodic'?)
>>>>
>>>> I'd really appreciate any help I can get with this; I'm very much out 
>>>> of my depth here...
>>>>
>>>> Thanks in advance!
>>>>
>>>> Matthew~
>>>>
>>>

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