Towards a working density-functional theory for polymers: First-principles determination of the polyethylene crystal structure

TL;DR

This paper applies a van der Waals density functional to accurately predict the crystal structure, cohesive energy, and elastic constants of polyethylene from first principles, showing good agreement with experimental data.

Contribution

It demonstrates the effectiveness of the vdW-DF functional in modeling polymer structures, advancing first-principles predictions for polymers.

Findings

Accurate prediction of polyethylene crystal structure.

Good agreement of elastic constants with experiments.

Validation of vdW-DF for polymer modeling.

Abstract

Equilibrium polyethylene crystal structure, cohesive energy, and elastic constants are calculated by density-functional theory applied with a recently proposed density functional (vdW-DF) for general geometries [Phys. Rev. Lett. 92, 246401 (2004)] and with a pseudopotential-planewave scheme. The vdW-DF with its account for the long-ranged van der Waals interactions gives not only a stabilized crystal structure but also values of the calculated lattice parameters and elastic constants in quite good agreement with experimental data, giving promise for successful application to a wider range of polymers.