Feature requested: local order parameters

[ZKC19940412]

As GPUMD massively upgrades its features, it will be nice to enable an on-the-fly computation of local order parameters. In essential, a local order parameter is used to identify the presence of different ice phases when one uses GPUMD to perform MD simulations on water/ice systems. Local order parameters can benefit various applications, such as probing ice nucleations. The functional form of order parameters mimics the spherical harmonics functions (more can be found in equations 1 and 2 in the reference paper), which are computed as the angular descriptors for NEP potential. Therefore, it should be very straightforward to may be added in a new "compute" keyword or include it in the "dump" keyword.

Please consider implementing this feature, and a reference paper can be found here: https://pubs.rsc.org/en/content/articlelanding/2011/cp/c1cp22167a

Thank you all so much.

Best,
Zekun

[brucefan1983]

Thanks for this good suggestion. We can consider enabling it in the near future.

[brucefan1983]

I have started looking at the literature. It seems there is a more general set of quantities as proposed in this paper:

Bond-orientational order in liquids and glasses

which is implemented in LAMMPS: https://docs.lammps.org/compute_orientorder_atom.html

Do you think this is a better choice? @ZKC19940412

[brucefan1983]

We aim to achieve this in GPUMD-v3.9.

[ZKC19940412]

Hi Bruce. Sorry for the late response. Yes. This reference in LAMMPS should be a good starting point. Thanks for working on it.

[brucefan1983]

@ZKC19940412 Thanks for confirming this. I have just released GPUMD-v3.8, and I will aim to add this feature to GPUMD-v3.9.