MEAM potential issue

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1

Dear LAMMPS Users,

I am wondering if anyone more skilled than me can figure out why I get an error using MEAM Library.

I am working on a Linux environment built including MEAM styles, trying to calculate the friction force between a Silicon tip and an Aluminium substrate.
I found the MEAM potentials between these 2 elements on library.meam along with AlSiMgCuFe.meam file.

Here is the portion of the code for achieving this task:

#####BASIC SETTINGS######

units metal
dimension 3
boundary p p p

#####ATOMS####

atom_style atomic
read_data data_lammps.in #input file

pair_style meam
pair_coeff * * library.meam AlS SiS AlSiMgCuFe.meam SiS SiS AlS AlS

in which I have 4 atom types (upper surface of the tip and rest of the tip, i.e. type 1,2; surface and bottom of the surface, i.e. type 3 and 4). I called the element AlS and SiS because in AlSiMgCuFe.meam it is specified that:

"MEAM Al, Si, Mg, Cu, Fe alloy potential. use with AlS SiS MgS CuS FeS from library.meam"

When I run the simulation a WARNING appears: "The pair_style meam command is unsupported. Please use pair_style meam/c instead ".

Therefore, I changed the pair style to meam/c, obtaining this ERROR: "MEAM library error 3".

I tried to modify the name of the elements in the library file (deleting the record with the same name) using the proper names (Al and Si) on the input file, but I got the same error.

The simulation runs anyway (using meam), but I'd like to be sure that the potential are accounted properly.

It looks like the tip's atoms are not really exerting any interaction forces on the aluminium surface even at a very little distance and I would like to discard the possibility of an issue related to the pair potentials.

Thank you for any help you will provide

Best regards

Andrea Mio, PhD

2

Dear LAMMPS Users,

I am wondering if anyone more skilled than me can figure out why I get
an error using MEAM Library.

​you get the error, because the ​AlSiMgCuFe.meam is written for the case of having 5 different extracted from library.meam, not 2 and in a specific order, too, as they are referred to inside the second meam parameter file by numerical indices. thus you have to change your pair_coeff line to what is written in the header of AlSiMgCuFe.meam:

pair_coeff * * library.meam AlS SiS MgS CuS FeS AlSiMgCuFe.meam SiS SiS AlS AlS

to reiterate: the first set of element labels extracts data sets from library.meam, the second meam file contains selected overrides to those parameters and then the final set of element labels selects parameter sets from this extracted and augmented parameter table to individual atom types.
this is a bit convoluted, but if you re-read the pair style meam documentation, you will find that it describes just that.

axel.