# Selective Nonthermal Melting in Phlogopite under Ultrafast Energy Deposition

## TL;DR

This study explores how phlogopite, a magnesium-rich mineral, responds to ultrafast energy input, revealing phase transitions and structural changes at different energy levels.

## Contribution

The paper introduces a novel hybrid computational model to study nonthermal melting in phlogopite under ultrafast energy deposition.

## Key findings

- At ∼0.17 eV/atom, hydrogen migration creates a superionic state in phlogopite.
- At ∼0.4 eV/atom, magnesium atoms diffuse within sublattices, indicating a phase transition.
- At ∼0.9 eV/atom, the bandgap collapses, making the material electronically conducting.

## Abstract

Phlogopite is a complex
magnesium-rich mineral from the dark mica
group, KMg3(AlSi3O10)­(OH)2. Its response to ultrafast excitation of its electronic system is
studied using a hybrid model that combines tight-binding molecular
dynamics with transport Monte Carlo and the Boltzmann equation. Simulations
predict that at the deposited dose of ∼0.17 eV/atom (electronic
temperature T
e ∼ 11,000 K), the
first hydrogens start to migrate in the otherwise preserved lattice,
transiently turning mica into a superionic state. At the dose of ∼0.4
eV/atom (T
e ∼ 13,000 K), Mg atoms
start to diffuse like a liquid within stable sublattices of other
elements, suggesting a superionic–superionic phase transition.
At a dose of approximately 0.5 eV/atom (T
e ∼ 14,000 K), the entire atomic lattice destabilizes, disordering
on a picosecond time scale. It is accompanied by the formation of
defect energy levels inside the bandgap. At the dose of ∼0.9
eV/atom (T
e ∼ 16,000 K), the bandgap
completely collapses, turning the material metallic (electronically
conducting). At even higher doses, nonthermal acceleration of atoms
heats the atomic system at ultrafast time scales; K and O elements
are most affected, accelerating within a few tens of femtoseconds.