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ab initio and QMC — Result In Brief

Project ID: 298150
Funded under: FP7-PEOPLE
Country: United Kingdom

From molecular to polymeric crystals

Conventional polymer synthesis involves gas- or liquid-phase polymerisation using a catalyst. EU-funded scientists explored a new approach: polymerisation of molecular crystals under pressure.
From molecular to polymeric crystals
Solid-state polymerisation can generate high-density polymers or single-crystal polymers. The process is initiated by ultrafast-laser-induced micro-explosions to attain extreme conditions. Under high pressure of the order of terapascal, the chemical bonds in molecular crystals are reconstructed, or the molecules rearranged.

Experiments aimed at compressing simple molecular crystals, such as nitrogen, carbon monoxide and hydrogen chloride, are still ongoing. This is largely due to the very little knowledge of the properties of these molecules under extreme conditions. Also, understanding the properties of the initial elements is necessary to understand the structures of compounds that may be formed.

The EU-funded project AB INITIO AND QMC (Phase transition and polymerization of molecular solids in ab initio calculations and quantum Monte Carlo simulations) aimed to fill this gap. The project team used ab initio random structure searching and quantum Monte Carlo algorithms to provide theoretical predictions needed in the synthesis of a new class of materials.

Project scientists predicted several stable phases of nitrogen at terapascal pressures. Among them is a layered structure that exhibits significant charge transfer. A metallic nitrogen salt is stable at high pressures and temperatures, and exhibits charge density distortions that were not expected in an element under extreme conditions.

The stability of the proposed exotic structures was established by computing their phonon spectra. The team's work has enhanced our understanding of chemical bonds under compression. They have also laid the groundwork to seek additional molecular crystals that can be transformed into extended solids and how to retain them at ambient conditions.

AB INITIO AND QMC findings have been described in a publication in the prestigious journal Physical Review Letters.

Related information


Polymerisation, catalyst, molecular crystals, terapascal, nitrogen, quantum
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