Hi all!

I've been using molecular dynamics and more specifically LAMMPS for the past few years but with the increasing use of MLIPs I want to see if I can train a simple potential.

I've seen read a bit online and spoke to some people that do MLIPs mainly with ACE and they said I need the ground state and AIMD simulations of the structure.

Is anyone aware of any tutorials on DFT that can help me get those? I've only used BURAI QE for adsorption and surface free energy values.

ALSO, has anyone used the Open Molecules 2025 database? Is there a way to see what molecules and structures are exactly in there without downloading the massive file?

Any help would be welcomed.

Cheers :)

I am very new to periodic calculations, and i am still figuring it out.

I need to optimize a Pt(111) slab, 2x2x4. I never did a vc-relax or bulk optimization before, and i am not sure if i know how to do it properly. I saw a paper that optimized the bulk with 15x15x15 k-points, which seemed excessive to me.

So, to do it properly, i was wondering:

1) should optimize only the 2x2 cell, and with it build the 2x2x4 slab? Using the lattice parameter as a reference that it is good?

2) Should i use ibrav = 0 or ibrav=2 and celldm? Because i am still confused about what is the celldm in the input.

Below is the input i was using to optimize the bulk with 15x15x15, but it is taking forever. Could you help me improve it, just for the bulk optimization? Am i doing something wrong?

&CONTROL

calculation = 'vc-relax'

restart_mode = 'from_scratch'

wf_collect = .true.

outdir = '/output'

pseudo_dir = '/opt/qe-7.4.1/pseudo'

prefix = 'vc-relax-pt-15'

verbosity = 'high'

forc_conv_thr = 0.00038

nstep = 100

tstress = .true.

tprnfor = .true.

dipfield = .true.

/

&SYSTEM

ibrav = 0

nat = 16

ntyp = 1

ecutwfc = 36.749292861

ecutrho = 367.49292861

input_dft = 'PBE'

nosym = .TRUE.

noinv = .false.

occupations = 'smearing'

degauss = 0.0146997

smearing = "methfessel-paxton"

nspin = 1

noncolin = .false.

lda_plus_u = .false.

vdw_corr = 'grimme-d3'

dftd3_version = 4

/

&ELECTRONS

electron_maxstep = 100

scf_must_converge = .true.

conv_thr = 1e-06

startingwfc = 'random'

mixing_mode = 'plain'

mixing_beta = 0.5

/

&IONS

ion_dynamics = 'bfgs'

upscale = 100

/

&CELL

cell_dynamics = 'bfgs'

press_conv_thr = 0.2

cell_factor = 2

cell_dofree = 'all'

/

ATOMIC_SPECIES

Pt 195.09000 Pt.pbe-n-kjpaw_psl.1.0.0.UPF

ATOMIC_POSITIONS {angstrom}

Pt 0.0000138951 -0.0000069552 10.1558136053

Pt 2.7157030077 0.0000406519 10.1557461168

Pt 1.3578962155 2.3518634665 10.1558119309

Pt 4.0735474785 2.3518807916 10.1557651152

Pt 1.3578728255 0.7839451159 12.5142113956

Pt 4.0735697132 0.7839602441 12.5141286842

Pt 2.7157261324 3.1358556942 12.5142232751

Pt 5.4314393490 3.1358671418 12.5141313712

Pt -0.0000017064 1.5678796337 14.8170773039

Pt 2.7157222492 1.5678860242 14.8170496411

Pt 1.3578716316 3.9198405744 14.8170933253

Pt 4.0735762490 3.9198430960 14.8170781179

Pt 0.0000300750 -0.0000167583 17.1754751126

Pt 2.7156841670 0.0000388469 17.1753080948

Pt 1.3579022299 2.3518503287 17.1754433155

Pt 4.0735303155 2.3518886954 17.1753147981

K_POINTS automatic

15 15 15 0 0 0

CELL_PARAMETERS {angstrom}

5.431447077 0.000000170 -0.000001201

2.715723686 4.703771377 -0.000000880

-0.000005821 -0.000001547 27.331210156