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Topological catastrophe and isostructural phase transition in calcium.
Travis E Jones1, Mark E Eberhart, Dennis P Clougherty
1Colorado School of Mines, Golden, Colorado 80401, USA. trjones@mines.edu
Physical Review Letters
|January 15, 2011
Summary
We predict a quantum phase transition in calcium (Ca) under pressure. A topological change in electron charge density at 80 kbar softens elastic modulus C
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Understanding phase transitions in elemental metals under pressure is crucial for materials science.
- The electronic topological transitions (ETTs) in metals can significantly alter their physical properties.
- Calcium (Ca) exhibits complex behavior under high pressure, making it a target for theoretical investigation.
Purpose of the Study:
- To predict and characterize a quantum phase transition in face-centered cubic (fcc) calcium under hydrostatic pressure.
- To investigate the topological changes in electron charge density and their correlation with elastic properties.
- To propose and validate an order parameter for the predicted phase transition.
Main Methods:
- Utilizing density functional theory (DFT) to model the electronic structure of fcc Ca.
- Analyzing the topology of the electron charge density using Bader analysis and bond path identification.
- Calculating elastic moduli (C' and C44) as a function of pressure.
- Applying Morse theory to the charge density to define an order parameter.
Main Results:
- A pressure-induced topological phase transition in fcc Ca is predicted at approximately 80 kbar.
- Below 80 kbar, charge density exhibits bifurcated bond paths; above 80 kbar, non-nuclear attractors form in octahedral holes.
- The transition is associated with a softening of the C' elastic modulus, while C44 remains unaffected.
- The proposed order parameter demonstrates mean-field scaling behavior near the critical pressure.
Conclusions:
- Fcc Ca undergoes a pressure-induced electronic topological transition, leading to a quantum phase transition.
- The observed changes in charge density topology directly influence the elastic anisotropy of Ca.
- The study provides a theoretical framework and order parameter for understanding pressure-induced phase transitions in metals.
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