Helical Organic and Inorganic Polymers.

Area of Science:

• Computational Chemistry
• Materials Science
• Polymer Physics

Background:

• Helical polymers are crucial in plastics and biomolecules but are understudied using advanced quantum chemical methods.
• Existing methods struggle with the complexity and incommensurable structures of infinite helical polymers.

Purpose of the Study:

• To develop and validate an *ab initio* computational framework for accurately characterizing infinite helical polymers.
• To enable the prediction of electronic, structural, and vibrational properties of these complex systems.
• To explore novel, potentially metastable helical polymers of nitrogen and oxygen.

Main Methods:

• Development of an *ab initio* second-order many-body Green's function [MBGF(2)] method tailored for helical polymers using symmetry-adapted Gaussian basis functions.
• Integration with density-functional theory (DFT) for energies, forces, and structural optimizations.
• Application to polyethylene, polyacetylene, and polytetrafluoroethylene to validate accuracy against experimental spectra and properties.

Main Results:

• The MBGF(2) method accurately predicts quasiparticle energy bands and vibrational frequencies, converging smoothly with oligomer results.
• The framework successfully characterizes both commensurable and incommensurable helical polymer structures.
• Validated accuracy of MBGF(2)/cc-pVDZ for photoelectron spectra and DFT for structures and vibrational spectra of model polymers.
• Predicted properties for novel nitrogen and oxygen helical polymers, including polyazene, polyazane, polyfluoroazane, and polyoxane.

Conclusions:

• The developed *ab initio* method provides a robust tool for studying infinite helical polymers.
• The study establishes the quantitative accuracy of the MBGF(2) approach for simulating polymer properties.
• Identified novel nitrogen and oxygen-based helical polymers as potential high-energy-density materials, warranting further investigation.