Vashista potential parameter info

GULP
1

Hello,

Now I try to study LD of SIN

To do this, I’d like to introduce vashishta potential.

So i found the details of example of SiO2 in the gulp library,

But I could not understand the parameter info in the each line of SiO2 vashishta in gulp library when i compare them with reference in SiO2 vashishta(Vashishta et al, Phys. Rev. B, 41, 12197 (1990))

Usually, vashishta potenital and their parameters are described as below:

image
image924×243 67.7 KB

but, i could not get infor , which line means the above parameter in the SiO2 vashishta in gulp library.

To get an understanding, I searched help file. but there is no description of vashishta.

Please, could I get the description of infor the implementaion of vashishta potential into gulp?

Sincerely yours.

2

You won’t find vashishta in the help file since it’s actually constructed from other existing potentials. You need to look up the commands in the library instead (i.e. lennard, general, sw3). If you compare these potentials to your expression then it’s just a bit of simple manipulation to equate the terms.

1 Like
3

Thanks for your valuable comment.
due to the comments, I could get understanding and transformation.
but. in the reference SiO2 vashishta(Vashishta et al, Phys. Rev. B, 41, 12197 (1990)), I could not find coulomb interaction term like below
image

among the options, if i write species like below:
ex)
species
A core 2
B core -1

then automatically do gulp introduce coulomb term of AA ,AB and BB ?
or is there any missing point?
i think the ref didn’t consider coulomb interaction fo rSiO2, so there no term about coulomb. However. i should consider this term…
i could not find help text about introducing coulomb interaction and could you recommend the potential type to consider image
?
Sincerely yours.

4

The Coulomb term is already there - if you compare the expression you give above you will see it’s the same as one of the potentials being used. If you add charges via species then this will introduce a term Zi.Zj/r which is not the Coulomb form used in Vashishta et al.

1 Like
5

Thanks for your comment, i could get image by editing general(m=1)

Then, if add the image term, can i erase the species line, because i add coulomb term by using general potential.?

Thanks

6

If you are trying to reproduce the model of Vashishta et al for silica from Phys. Rev. B, 41, 12197 (1990) then use the library file “as is” since this does have a standard Coulomb term. If you are trying to reproduce a different model that only has Coulomb interaction multiplied by exponential decay then do not use species as this will invoke the standard Coulomb term.