# Some questions in the NEB example.

Chris K. Lee lksz... at gmail.com
Thu Jun 29 06:04:37 UTC 2017

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Dear CP2K users,

I have some questions in the NEB example.

(*https://www.cp2k.org/exercises:2015_cecam_tutorial:neb*
<https://www.cp2k.org/exercises:2015_cecam_tutorial:neb>)

It’s so hard to understand only with the Input reference.

(*https://manual.cp2k.org* <https://manual.cp2k.org/>)

At ./NEB/EX2/neb_GPW.inp

1. line 2

&MULTIPLE_FORCE_EVALS

FORCE_EVAL_ORDER 2 3

“FORCE_EVAL_ORDER {Integer} ...” : Specify the orders of the different
force_eval.

What does ‘orders’ mean? What I guess for ‘2 3’ is

There are three FORCE_EVAL sections and 1st one only contains the
information.

The 2nd and 3rd ones act as usual ‘FORCE_EVAL’. Am I right?

2. line 9

&FORCE_EVAL / &MIXED

GROUP_PARTITION 2 16

“GROUP_PARTITION {Integer} ...” : gives the exact number of processors for
each group

Is this mean that using 2 cpu processors for the 2nd FORCE_EVAL and 16 for
the 3rd one?

At ./NEB/EX2/neb.inp ‘GROUP_PARTITION 1 1’ means it only use total 2
processors?

3. line 12, 13

&FORCE_EVAL / &MIXED / &GENERIC

MIXING_FUNCTION E1+E2

VARIABLES E1 E2

What does these two terms mean and how it works?

Is this ‘VARIABLES’ only for energy?

Does the CP2K understands that the variables as energy of 2nd and 3rd
FORCE_EVAL?

Which energy would be printed on the output?

4. line 24, 27

&FORCE_EVAL / &MIXED / &MAPPING

&FORCE_EVAL 1 , &FORCE_EVAL 2

Does it mean that the 2nd FORCE_EVAL would treated as ‘1’ and the 3rd one
as ‘2’ ?

5. line 33

&FORCE_EVAL / &SUBSYS

&COLVAR

Does this ‘COLVAR’ make automatically its own output without PRINT options?

6. line 72

&FORCE_EVAL / &MM / &FORCEFIELD / &NONBONDED / &GENPOT

atoms Cu C

FUNCTION A*exp(-av*r)+B*exp(-ac*r)-C/(r^6)

VARIABLES r

“VARIABLES {Word} ... “ : Defines the variable of the functional form.

It shows they are trying to use ‘r’ as variable but that’s all.

Does CP2K understand that ‘r’ as distance between Cu and C?

Only the distance should be the ‘variables’ here?

7. line 213

&MOTION / &BAND

NPROC_REP 18

Is this option useless for the serial run like ssmp?

8. REPLICAs

What I under stand is that they used the intermediate coordinates as
replica.

They already optimized geometry for starting materials and final products.

How they get the optimized intermediate coordinates of the replica?

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