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Re: [lammps-users] Pair_style hybrid
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Re: [lammps-users] Pair_style hybrid


From: Michał Kański <michal.kanski@...2460...>
Date: Thu, 24 Aug 2017 13:17:00 +0000

You should search literature for similar systems and check what potentials were used. For questions about potential validation you should contact a local advisor, since this mailing list is for providing support with LAMMPS issues.

What do you mean by “potential fails”? If your system behaves abnormally, it may be caused by wrong potentials, but also by too high timestep or bad initial geometry.

 

Michal

 

From: Kousika A
Sent: czwartek, 24 sierpnia 2017 11:43
To: Michał Kański
Cc: LAMMPS Users Mailing List
Subject: Re: [lammps-users] Pair_style hybrid

 

Thank you Michal. I have few more doubts. If I am using a hybrid potential, how to check the reliability of the potential for that system? Other than it's lattice parameter and bulk modulus, do we need to check any other things?

I have got results for lattice parameter and bulk modulus comparable with the reported values (@0K) But when I am bringing the system to 300K, the potential fails. How to fix this? 

 

Thanking you,

Kousika

 

On Wed, Aug 23, 2017 at 8:22 PM, Michał Kański <michal.kanski@...2460...> wrote:

This is the way LAMMPS is designed – pair_style is defined for an entire system and if you want to utilize different potentials at once you have to use pair_style hybrid.

 

Michal

 

From: Kousika A
Sent: środa, 23 sierpnia 2017 15:36
To: Michał Kański
Cc: LAMMPS Users Mailing List
Subject: Re: [lammps-users] Pair_style hybrid

 

Thank you Michal. But I am using single pairstyle for each pair. For some pairs only Morse and for others, only coul like that. So how come overwritten will happen?

 

 

 

On Wed, Aug 23, 2017 at 6:37 PM, Michał Kański <michal.kanski@...2460...> wrote:

In the first one each pair_style command overwrites earlier ones. The second one allows for using different pair_styles alongside.

 

Michal

 

From: Kousika A
Sent: środa, 23 sierpnia 2017 14:42
To: LAMMPS Users Mailing List
Subject: [lammps-users] Pair_style hybrid

 

Dear lammps users,

                                 I am modeling a quaternary system. I am using two different pair styles, Morse and coul/wolf for the interactions. What is the difference if I am giving the interactions separately like in (1) or giving using hybrid command as in (2)

 

(1)

pair_style morse 6.0 

pair_coeff 1 3 0.5799 2.232 2.737 6  #Ba-O 

pair_coeff 1 4 0.858 2.33 2.677 6   #Ba-N

  

pair_coeff 2 3 2.3667 2.087 1.855   #Ta-O

pair_coeff 2 4 1.7369 2.16 1.987   #Ta-N

#pair_coeff 3 3 5.116 2.6796 1.208 # O-O

#pair_coeff 4 4 9.904 2.85 1.08 #N-N

#pair_coeff 3 4 6.623 2.83 1.159 #O-N

 

pair_style coul/wolf 0.3367 10

pair_coeff 1 1 

 

pair_style coul/wolf 0.402 10

pair_coeff 1 2 

 

pair_style coul/wolf 0.4975 10

pair_coeff 2 2 

 

pair_style coul/wolf 0.913 10

pair_coeff 3 3 

 

pair_style coul/wolf 0.888 10

pair_coeff 4 4 

 

pair_style coul/wolf 0.507 10

pair_coeff 3 4 

 

 

(2)

 

pair_style hybrid morse 10.0 coul/wolf/mod 0.3367 10 coul/wolf/mod 0.402 10 coul/wolf/mod 0.4975 10 coul/wolf/mod 0.913 10 coul/wolf/mod 0.888 10 coul/wolf/mod 0.507 10

pair_coeff 1 3 morse 0.5799 2.232 2.737  #Ba-O 

pair_coeff 1 4 morse 0.858 2.33 2.677    #Ba-N

  

pair_coeff 2 3 morse 2.3667 2.087 1.855   #Ta-O

pair_coeff 2 4 morse 1.7369 2.16 1.987   #Ta-N

 

pair_coeff 1 1 coul/wolf/mod 1

 

pair_coeff 1 2 coul/wolf/mod 2

 

pair_coeff 2 2 coul/wolf/mod 3

 

pair_coeff 3 3 coul/wolf/mod 4

 

pair_coeff 4 4 coul/wolf/mod 5

 

pair_coeff 3 4 coul/wolf/mod 6

 

Kindly clarify this.

 

Thanking you,

Kousika