[QE-users] Regarding initialization of elastic constants for NEB code

[Jana, Soumyajit]

Also,

One thing that I noticed is that the suggested values of k_max and k_min is highly dependent on the value of 'ds' . I am not exactly sure what that term does.

Soumyajit

From: Jana, Soumyajit
Sent: Thursday, October 10, 2019 7:30 AM
To: tone.kokalj at ijs.si; Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] Regarding initialization of elastic constants for NEB code

Hi,
Is there any way to initialize spring constants based on the type of material I am using?
Soumyajit
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________________________________
From: users <users-bounces at lists.quantum-espresso.org<mailto:users-bounces at lists.quantum-espresso.org>> on behalf of Tone Kokalj <tone.kokalj at ijs.si<mailto:tone.kokalj at ijs.si>>
Sent: Thursday, October 10, 2019 12:59:16 AM
To: users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org> <users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>>
Subject: Re: [QE-users] Regarding initialization of elastic constants for NEB code

On Thu, 2019-10-10 at 00:21 +0000, Jana, Soumyajit wrote:
> Hi,
>
> I am using NEB code to calculate vacancy jump activation energy in
> pure copper. I am not sure how to initialize elastic constants  (
> k_max and k_min)

Here is a simple empirical recommendation based on my experience: do
not initialize them, but rely on default values - they are OK for most
purposes (K_max and k_min are not really that crucial). But if you want
to initialize them nevertheless, then your k_max is OK, but k_min
appears too tiny, use something like 0.1 instead.

Regards, Tone
--
Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
(tel: +386-1-477-3523 // fax: +386-1-251-9385)


>
> BEGIN
> BEGIN_PATH_INPUT
> &PATH
>    restart_mode  = 'from_scratch'
>    string_method  = 'neb'
>    nstep_path     = 55
>    num_of_images  = 9
>    opt_scheme     = 'broyden'
>    CI_scheme      = 'auto'
>    path_thr       = 0.05
>    k_max          = 0.3
>    k_min          = 0.001
>    ds             = 0.1
>    first_last_opt = .false.
>    minimum_image  = .true.
>    use_freezing   = .true.
>    use_masses     = .true.
> /
> END_PATH_INPUT
>
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