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Updated: Jan 27, 2026

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction
Published on: April 10, 2018
Pressure-induced spin transition and site-selective metallization in CoCl2
Jose A Barreda-Argüeso1, Lucie Nataf2, Fernando Aguado1
1Universidad de Cantabria, MALTA Consolider Team - DCITIMAC, Santander, 39005, Spain.
High pressure transforms cobalt chloride (CoCl2) into a metallic state, inducing a spin crossover in cobalt ions. This metallic phase coexists with localized magnetism before full electron delocalization.
Area of Science:
- Condensed Matter Physics
- Materials Science
- High-Pressure Physics
Background:
- Cobalt chloride (CoCl2) exhibits complex electronic and magnetic properties under extreme conditions.
- Understanding spin-state transitions and metallization is crucial for novel material design.
Purpose of the Study:
- To investigate the pressure-induced metallization and spin crossover in CoCl2.
- To elucidate the relationship between electronic band gap closure and magnetic spin states.
Main Methods:
- Combined experimental techniques: X-ray diffraction, electrical resistivity, and spectroscopy.
- Theoretical calculations: Ab-initio computations under high-pressure conditions.
Main Results:
- Observed pressure-induced metallization and a spin crossover from high-spin (S=3/2) to low-spin (S=1/2) Co2+ near 70 GPa.
- Metallization is linked to p-d charge-transfer band gap closure, preserving localized 3d electrons.
- Coexistence of metallization and localized Co2+ low-spin magnetism confirmed up to 180 GPa.
Conclusions:
- CoCl2 exhibits a unique pressure-induced phase where metallization and localized magnetism coexist.
- This phenomenon precedes the full 3d-electron delocalization and Mott-Hubbard breakdown at higher pressures.
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