How to set box.raw for hexagonal lattice

[mcourtiel]

Hi everyone,

I'm currently working with DeepMD-kit v2.2.10 on a periodic system with a hexagonal lattice, but I'm struggling with the box definition in box.raw.

The system has the following box parameters:

• A = B = 15.297 Å, C = 11.219 Å
• α = β = 90.0°, γ = 120.0°

I've tried two different representations for box.raw (xx xy xz yx yy yz zx zy zz):

1. 15.297 0 0 −7.6485 13.2476 0 0 0 11.219
2. 7.6485 -13.2475906 0 7.6485 13.2475906 0 0 0 11.219 (from CASTEP)

In both cases, I get exactly the same fitting on 1000 frames:

For comparison, I also trained on a similar system in a cubic box:

• A = B = C = 16 Å, α = β = γ = 90.0°
• box.raw = (16 0 0 0 16 0 0 0 16)

The fitting is better (not perfect since it's trained on 250,000 steps with only 400 frames):

Could someone help me understand what I'm doing wrong with the hexagonal lattice? Any insights would be greatly appreciated!

Thanks in advance!

[njzjz]

You should use the same box as that in the DFT calculation.

[mcourtiel]

It is exactly what I have done..It is illustrated in the first case of my previous message.

Also I did now an other test, I took my system (wich is in an hexagonal lattice) and converted it in an othorombic lattice, and this is fitting well, so I think there is a problem coming from the hexagonal case.

[njzjz]

I think you could do a simple test: using the same model, do the structures before and after you convert give the same result?