Some confusion about vashishta potential of alumina

LAMMPS LAMMPS Beginners
1

Dear all，

Recently, I have been trying to study some properties of alumina properties using LAMMPS. However, I encountered issues while employing the vashishta potential for alumina.

Despite my efforts, I have been unable to locate the potential function file for the vashishta potential of alumina. As an alternative, I analyzed the vashishta potential file of SiC from LAMMPS and adjusted the parameters based on the information provided in the article “J. Appl Phys 103, 083504 (2008)” (https://doi.org/10.1063/1.2901171). Concurrently, I considered the revisions of the D values in the original literature “J. Appl Phys 105, 059901 (2009)” (https://doi.org/10.1063/1.3099561).

The modified potential file contains the following content.

other quantities are unitless

Note: Value of D here equals D/2 in paper

element1 element2 element3

H eta Zi Zj lambda1 D lambda4

W rc B gamma r0 C cos(theta)

Al Al Al 12.7506 7 1.5237 1.5237 5.0 0.0 3.75
0.0 6.0 0.0 0.0 0.0 0.0 0.0

O O O 564.7334 7 −1.0158 −1.0158 5.0 321.40849 3.75
79.2884 6.0 0.0 0.0 0.0 0.0 0.0

O Al Al 249.3108 9 −1.0158 1.5237 5.0 361.58482 3.75
0.0 6.0 8.1149 1.0 2.90 10.0 -0.333333333333

Al O O 249.3108 9 1.5237 -1.0158 5.0 361.58482 3.75
0.0 6.0 12.4844 1.0 2.90 10.0 0.0

O O Al 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0

O Al O 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0

Al O Al 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0

Al Al O 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.0

However, upon attempting to calculate the energy variance from the alpha-alumina to gamma-alumina transition, the obtained value is several hundred eV/formula.unit, which is evidently inaccurate. Therefore, I would like to seek assistance to confirm where the issue lies.

Thank you in advance.

2

This is close to unreadable, since you didn’t quote the file correctly. The forum text engine uses markup through special characters to allow typesetting and thus to have properly quoted text it needs to be bracketed with triple backquotes (```). Please see the forum guidelines and suggestions post for more details.

This is obviously an error with your input, be it the potential file, be it the input geometry and further commands. It is impossible to give meaningful advice without knowing more details and being involved in your work. So, as with most tasks in science, you will have to confirm for yourself that each bit of data, each command, each parameter is chosen in a suitable way.

This forum is not an “input debugging service” and thus you will have to do this yourself.

As for the potential file, its format and the meaning of the individual values are documented in the LAMMPS manual page for the vashishta pair style.

4

Thank you for your response. I’ve identified the reason for the discrepancy, which stems from an error in my unit conversion. and I’ll also make sure to read the community guidelines to improve my questioning skills. :blush:

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5

Hello Tim,

I am looking to use this same Vashishta potential for Al2O3;

Where did you find/locate the potential file/parameters? I cannot seem to find it anywhere

Thank you

6

He provided links to paper and you can download format from NIST potential repository and use the template.

7

I have a question, will this potential model able to capture gamma alumina model. I am trying to model gamma alumina.

8

You have to study the corresponding publication or make tests or both.

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