Theoretical and computational study of high-pressure structures in barium
1Department of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ, United Kingdom.
Physical Review Letters
|September 16, 2000
Summary
Elemental barium forms a unique high-pressure structure (Ba IV) with two interpenetrating lattices. Calculations confirm its stability and potential disorder, linked to close-packed structure instabilities.
Area of Science:
- Condensed Matter Physics
- Materials Science
- High-Pressure Physics
Background:
- Elemental barium exhibits a complex high-pressure phase (Ba IV).
- This structure uniquely involves two interpenetrating incommensurate lattices, unlike typical elemental structures.
- The nature and stability of this self-hosting structure require further investigation.
Purpose of the Study:
- To investigate the stability and structural characteristics of the high-pressure barium phase (Ba IV).
- To understand the underlying mechanisms leading to the formation of this unusual two-lattice structure.
- To explore the potential for similar structures in other divalent elements.
Main Methods:
- Utilizing pseudopotential calculations to model the electronic structure and stability.
- Analyzing band structures and applying nearly free electron theory.
- Identifying vibrational modes to assess structural stability.
Main Results:
- Pseudopotential calculations confirm the stability of the Ba IV structure.
- The calculations suggest a potentially disordered nature of the 'guest' lattice within Ba IV.
- A zero-energy vibrational mode was identified, indicating a soft mode associated with the phase transition.
- The formation of Ba IV is linked to an instability in the close-packed structure.
Conclusions:
- The high-pressure Ba IV structure of elemental barium is theoretically stable.
- The unique two-lattice structure arises from an instability in conventional close-packed arrangements.
- Further research could explore the stability of similar incommensurate structures in other divalent elements.
More Related Videos
10:52Conducting Elevated Temperature Normal and Combined Pressure-Shear Plate Impact Experiments Via a Breech-end Sabot Heater System
Published on: August 7, 2018
08:00Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain
Published on: March 27, 2018
Related Concept Videos
02:57Definition and Measurement of Pressure: Atmospheric Pressure, Barometer, and Manometer
Gas pressure is caused by force exerted by gas molecules colliding with the surfaces of objects. Although the force of each collision is very small, any surface of an appreciable area experiences a large number of collisions in a short time, which can result in high pressure.
01:10Van der Waals Equation
The ideal gas law is an approximation that works well at high temperatures and low pressures. The van der Waals equation of state (named after the Dutch physicist Johannes van der Waals, 1837−1923) improves it by considering two factors.
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
01:18Variation of Atmospheric Pressure
Change in atmospheric pressure with height is particularly interesting. The decrease in atmospheric pressure with increasing altitude is due to the decreasing gravitational force per unit area as we move away from the surface of the earth.
Assuming the air temperature is constant at a given altitude and that the ideal gas law of thermodynamics describes the atmosphere to a good approximation, one can find the variation of atmospheric pressure with height.
Let p(y) be the atmospheric pressure at...
Assuming the air temperature is constant at a given altitude and that the ideal gas law of thermodynamics describes the atmosphere to a good approximation, one can find the variation of atmospheric pressure with height.
Let p(y) be the atmospheric pressure at...
01:13Excess Pressure Inside a Drop and a Bubble
The shape of a small drop of liquid can be considered spherical, neglecting the effect of gravity. This drop can further be considered as two equal hemispherical drops put together due to surface tension. The forces acting on the spherical drop are due to the pressure of the liquid inside the drop, the pressure due to air outside the drop, and the force due to the surface tension acting on the two hemispherical drops.
01:15Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Deformation occurs in axial and transverse directions when an axial load is applied to a slender bar. This deformation impacts the cubic element within the bar, transforming it into either a rectangular parallelepiped or a rhombus, contingent on its orientation. This transformation process induces shearing strain. Axial loading elicits both shearing and normal strains. Applying an axial load instigates equal normal and shearing stresses on elements oriented at a 45° angle to the load axis.
01:26The Van der Waals Equation
The ideal gas law is based on two simplifying assumptions: first, that there are no intermolecular attractions between gas molecules, and second, that the volume occupied by the molecules themselves is negligible compared with the volume of the container. However, these assumptions don't hold up under all conditions - specifically, at high pressures and low temperatures, as gas tends to deviate from ideal gas behavior.The van der Waals equation is an enhanced version of the ideal gas law,...