Improving density functional theory for crystal polymorph energetics.

Area of Science:

• Computational Chemistry
• Materials Science
• Solid-State Physics

Background:

• Density Functional Theory (DFT) is widely used for predicting material properties.
• Accurate prediction of crystalline polymorph relative stabilities is crucial in materials science.
• Previous DFT studies showed significant variability in predicting para-diiodobenzene (PDIB) polymorph stability.

Purpose of the Study:

• To improve the accuracy of DFT predictions for the relative stabilities of PDIB polymorphs.
• To validate a simple two-body correction method using wavefunction-based electronic structure theory.
• To compare computational results with experimental data and benchmark quantum Monte Carlo (QMC) calculations.

Main Methods:

• Employed a two-body correction scheme incorporating Grimme's spin-scaled second-order Møller-Plesset perturbation theory (MP2).
• Applied the corrected scheme in conjunction with various density functionals for DFT calculations.
• Calculated the relative stabilities of the two known ambient polymorphs of para-diiodobenzene (PDIB).

Main Results:

• The two-body corrected DFT scheme dramatically improved the prediction quality for PDIB polymorph stabilities.
• The corrected method consistently predicted the alpha-polymorph as more stable, in agreement with experimental observations.
• The calculated relative stability closely matched benchmark Quantum Monte Carlo (QMC) results within statistical uncertainty.

Conclusions:

• A simple two-body correction significantly enhances DFT accuracy for crystalline polymorph relative stabilities.
• The improved method provides reliable predictions for PDIB polymorph stability, consistent with experimental and high-level theoretical data.
• This approach offers a more robust computational tool for predicting the behavior of crystalline materials.