Designing accurate Moment Tensor Potentials for Phonon‐ related Properties of Crystalline Polymers

Structure of the data

VASP training data generation. The training data for the MTPs is generated in these active learning runs.

PE

split into segments 15 K – 30 K, 30 K - 150 K, 150 K - 300 K, 300 K - 400 K and 400 K - 500 K

PT

15-500 K

 P3HT

15 K – 300 K, 300 K – 400 K and 400 K – 500 K

Moment Tensor Potential (MTP) main training runs. Typically 5 training runs with different random initialisations are performed, which are labelled with a, b, c, d and e.

 PE MTP_MD

a, b, c, d ("best"), e

PE MTP_phonon

a, b, c, d ("best"), e

PT MTP_MD

a, b, c ("best"), d, e

PT MTP_phonon

a, b ("best"), c, d, e

P3HT MTP_MD

a, b, c, d ("best"), e

P3HT MTP_phonon

a, b ("best")

VASP validation runs. VASP active learning runs are performed at 300 K in an NPT ensemble. The resulting data is used to determine RMSD_MD and for the comparisons in Section 2.8 "Energy, Force and Stress in Molecular Dynamics".

PE. This run is also used in the section "Energy, Force and Stress in Molecular Dynamics"

PT

P3HT

MTP further training runs. These are various other training runs that resulted in the MTPs in Section 2.2. "Impact of the Choice of the Reference Data, the Level of the MTP, and the Number of Considered Atom Types"

temperature ranges. see Figure 4a and 4b.

15-100 K, 15-200 K 15-300 K, 15-400 K each for PE and PT

15-500 K is identical to MTP_MD and can be found in folder MTP_main_training_runs

Levels

Level 18

Level 22 is identical to the 15-100 K training run in the folder MTP_further_training_runs/temperature_ranges

Level 26 is identical to MTP_phonon and can be found in the folder MTP_main_training_runs

 Atom type splitting for P3HT

1 carbon type, i.e. no splitting

3 carbon types

6 carbon types 

Relaxations

Relaxed unit cells

Relaxed unit cells of the DFT calculations and of the "best" MTP_MD and "best" MTP_phonon. These are the unit cell that are used to calculate e.g. phonon band structures.

DFT Relaxations

Unit cell and atomic relaxations of PE, PT and P3HT. For descriptions of the relaxation procedure we refer to the Method and Introduction section of the main paper and Section S1 of the Supplementary Materials

Elastic constants calculations

DFT (main calculation with high energy cutoff)

MTP_MD

PE, PT, P3HT

clamped ion method (as shown in main paper)

strain distance 1 % (used in main paper), 0.1 % and 0.01 %. (0.1 % and 0.01 % are a convergence test)

as above, MTPs with different random initialisations are labelled a, b, c, d, e.

relaxed ion method (as shown in Supplementary Materials)

MTP_phonon

same folder structure as for MTP_MD

DFT with low 400 eV energy cutoff

Phonon calculations

DFT

MTP_phonon

PE, PT, P3HT

best (in terms of RMSD_phonon)

median (in terms of RMSD_phonon)

MTP_MD

PE, PT, P3HT

best (in terms of RMSD_MD)

AIREBO

Thermal conductivity calculations

DFT

displacement 0.03 Å (main calculation)

RTA, 10×15×160 q-mesh

full BTE, 10×15×60 q-mesh

full BTE, 4×6×160 q-mesh

displacement 0.05 Å (convergence test)

MTP_phonon

a, b, c, d ("best"), e

RTA, 10×15×160 q-mesh

full BTE, 10×5×60 q-mesh

full BTE, 4×6×160 q-mesh

Thermal Expansion

MTP_MD

a, b, c, d ("best"), e

AIREBO

Energy, Force and Stress in Molecular Dynamics

MTP_MD

AIREBO

Validation MD active learning run at 300 K is contained in the folder VASP_validation_runs/PE

A Note on axis relabelling

In order to align the three materials PE, PT and P3HT consistently, such that the polymer chain is always in z-direction, we relabelled the axis for the paper in the following way:

PE

x --> z

y --> y

z --> x

PT

x --> y

y --> x

z --> z

P3HT

x --> z

y --> y

z --> x

Example

The q-mesh for the phono3py calculation of PE is given as 160×15×10 in the job-submission-script where phono3py is called, but in the paper (and above) it is written as 10×15×160. All calculations (including POSCAR files etc.) are consistent with each other in terms of their axis labels. Just for the paper, the axis relabelling was performed.