QM/MM with missing FF parameters

[Léon Luntadila Lufungula]

Dear all,

I want to set up a QM/MM calculation wherein I describe a TiO2 slab with xTB and the water layer above and below the slab with the TIP3P water model, but I am wondering if this is even possible. I tried a quick test QM/MM calculation wherein I combined my xTB setup which worked for the slab in vacuum and my TIP3P setup which worked with a box of water and combined it with a QM/MM part adapted from this tutorial. However, upon running the calculation, CP2K fails because of missing FF parameters between Ti and O. So I was just wondering if it is even possible to do this without a FF that also has parameters between Ti and the MM atoms? 

Note: I did set the CELL in SUBSYS and the one in QMMM to the same box. I don't know if this might pose a problem, but I didn't know how to choose a cell that is in the middle of the subsys cell, so I quickly set both to the same just to be able to perform the test.

Any help/suggestions would be greatly appreciated!

Thanks in advance,

Léon

[Léon Luntadila Lufungula]

Dear all,

This might have been a stupid question, but could someone confirm/deny if it is possible to do a QM/MM calculation with only FF parameters for the MM atoms without FF parameters for the QM atoms? I just want to know if I have to keep working on getting this to work or look into other possible routes (going fully QM or looking for parameters for the interactions of the Ti atoms)?

Kind regards,

Léon

[Jürg Hutter]

Hi

you will need at least the parameters for the interaction MM atoms to
QM atoms

regards
JH

________________________________________
From: cp...@googlegroups.com <cp...@googlegroups.com> on behalf of Léon Luntadila Lufungula <Leon.luntad...@uantwerpen.be>
Sent: Tuesday, January 16, 2024 11:43 AM
To: cp2k
Subject: [CP2K:19757] Re: QM/MM with missing FF parameters

Dear all,

This might have been a stupid question, but could someone confirm/deny if it is possible to do a QM/MM calculation with only FF parameters for the MM atoms without FF parameters for the QM atoms? I just want to know if I have to keep working on getting this to work or look into other possible routes (going fully QM or looking for parameters for the interactions of the Ti atoms)?

Kind regards,
Léon

On Monday 15 January 2024 at 16:55:11 UTC+1 Léon Luntadila Lufungula wrote:
Dear all,

I want to set up a QM/MM calculation wherein I describe a TiO2 slab with xTB and the water layer above and below the slab with the TIP3P water model, but I am wondering if this is even possible. I tried a quick test QM/MM calculation wherein I combined my xTB setup which worked for the slab in vacuum and my TIP3P setup which worked with a box of water and combined it with a QM/MM part adapted from this tutorial<https://www.cp2k.org/exercises:2018_ethz_mmm:qmmm_2018>. However, upon running the calculation, CP2K fails because of missing FF parameters between Ti and O. So I was just wondering if it is even possible to do this without a FF that also has parameters between Ti and the MM atoms?

Note: I did set the CELL in SUBSYS and the one in QMMM to the same box. I don't know if this might pose a problem, but I didn't know how to choose a cell that is in the middle of the subsys cell, so I quickly set both to the same just to be able to perform the test.

Any help/suggestions would be greatly appreciated!

Thanks in advance,
Léon

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[Léon Luntadila Lufungula]

Hi Prof. Hutter,

Thanks for the prompt reply! I was afraid that this was indeed the case... I'm still a novice when it comes to force fields, but I understand that FF parameters for Ti atoms are not that common... I tried using ambertools to get parameters for the interactions of Ti but this also did not seem to work... Do you (or anybody else for that matter) know if there is a way to get such parameters or is it hopeless to try QM/MM with Ti atoms present in the system?

Kind regards,

Léon

[Jürg Hutter]

Hi

have you tried Google Scholar? A search for "TiO2 force fields"
gives 100s of recent results for TiO2 interacting with water
and biomolecules.

regards
JH

________________________________________
From: cp...@googlegroups.com <cp...@googlegroups.com> on behalf of Léon Luntadila Lufungula <Leon.luntad...@uantwerpen.be>

Sent: Tuesday, January 16, 2024 3:21 PM
To: cp2k
Subject: Re: [CP2K:19759] Re: QM/MM with missing FF parameters

To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/7211e3fb-17d8-4978-a2ec-89f5f633c5can%40googlegroups.com<https://groups.google.com/d/msgid/cp2k/7211e3fb-17d8-4978-a2ec-89f5f633c5can%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Léon Luntadila Lufungula]

Dear Prof. Hutter,

You are indeed correct, that was an oversight on my account! I'll look into the articles to see if I can find suitable parameters for all atom pairs in my system as I also intend to graft phosphonic acids onto the TiO2 surface.

Kind regards,

Léon