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### Vacancy migration frequency

Posted: **Sun Dec 08, 2019 4:33 pm**

by **Chaure**

Dear users,

If I calculate energy barrier for vacancy migration, How Can one calculate vacancy migration frequency ?

Sincerely

### Re: Vacancy migration frequency

Posted: **Sun Dec 08, 2019 5:41 pm**

by **graeme**

Within the harmonic approximation, you need to calculate the normal mode frequencies at the reactant and saddle point. Then the attempt frequency for hopping is given by: v = Prod v_rs / Prod v_ts , where Prod is the product of all the positive frequencies v = w/2pi, rs is the reactant state and ts is the saddle point.

### Re: Vacancy migration frequency

Posted: **Sun Dec 08, 2019 8:58 pm**

by **Chaure**

Dear Professor,

Is there any link to calculate normal mode frequency at reactant and saddle point?

Sincerely

### Re: Vacancy migration frequency

Posted: **Sun Dec 08, 2019 9:18 pm**

by **graeme**

### Re: Vacancy migration frequency

Posted: **Mon Dec 09, 2019 2:12 pm**

by **Chaure**

Dear Professor,

Can we use the INCAR tags to run vibrational frequency like IBRION = 5 or 6 in the same NEB run. Also Do we need to set selective dynamics like calculating mode in one direction like z.

Sincerely

### Re: Vacancy migration frequency

Posted: **Mon Dec 09, 2019 2:15 pm**

by **graeme**

You are able to freeze atoms using the selective dynamics tags. Keep those same setting for the dynamical matrix calculation.