Spherical Cell

Diego Gomez

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Jan 5, 2021, 2:47:29 PM1/5/21

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I'm trying to run a gas phase cluster calculation in CP2K. I want to create an outside force to force water molecules that are in the simulation within a radius of a central ion. I want to create a spherical cell of a given radius λ, fix the ion in the center and then run QMMD using the waters.

Does anyone know how to create a spherical cell or a better way to impose this clustering constraint λ?

Thomas Kühne

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Jan 5, 2021, 2:54:22 PM1/5/21

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Ciao Diego,

you may try to use a distance restraint. The former can be specified in FORCE_EVAL/SUBSYS/COLVAR

and the latter enforced via MOTION/CONSTRAINT/COLLECTIVE/RESTRAINT.

Greetings,

TDK

Am 05.01.2021 um 20:47 schrieb Diego Gomez <diego.g...@gmail.com>:

I'm trying to run a gas phase cluster calculation in CP2K. I want to create an outside force to force water molecules that are in the simulation within a radius of a central ion. I want to create a spherical cell of a given radius λ, fix the ion in the center and then run QMMD using the waters.
Does anyone know how to create a spherical cell or a better way to impose this clustering constraint λ?

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Thomas D. Kühne

Dynamics of Condensed Matter

Chair of Theoretical Chemistry

University of Paderborn

Warburger Str. 100

D-33098 Paderborn

Germany

tdku...@mail.upb.de

+49/(0)5251/60-5726

Diego Gomez

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Jan 19, 2021, 4:38:06 PM1/19/21

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Thomas,

I appreciate your response and after reading CP2K manual I absolutely agree with suggestion, however I am struggling with doing this operationally, do you happen to have an .inp file that you could show me or provide some guidance.

Thank you,

Diego

Marcella Iannuzzi

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Jan 20, 2021, 3:29:08 AM1/20/21

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Dear Diego

One can add an EXTERNAL_POTENTIAL acting only on a list of atoms.

Choosing the analytical form you can tune the range and the strength.

Something like

C*(1-(1-(sqrt(x^2+y^2+z^2)/R0)**n)/(1-(sqrt(x^2+y^2+z^2)/R0)**m))

should work.

Kind regards

Marcella

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