Structural, electronic, and vibrational properties of high-density amorphous silicon: a first-principles...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Low-density amorphous silicon (LDA) typically features a tetrahedral network.
• High-density amorphous silicon (HDA) is formed by compressing LDA silicon.
• Understanding the structural and electronic properties of amorphous silicon phases is crucial.

Purpose of the Study:

• To investigate the structural, electronic, and dynamical properties of high-density amorphous (HDA) silicon.
• To compare HDA silicon with low-density amorphous (LDA) silicon.
• To elucidate the relationship between structural distortions and material properties in amorphous silicon.

Main Methods:

• First-principles calculations were employed to study HDA silicon.
• Analysis of structural differences, electronic density of states (EDOS), and vibrational density of states (VDOS).
• Comparison of calculated properties with experimental findings.

Main Results:

• HDA silicon possesses a highly distorted tetrahedral network, contrasting with LDA's regular tetrahedral structure.
• The coordination number of HDA silicon is approximately 5, significantly higher than LDA.
• HDA silicon exhibits metallic behavior, supported by electronic density of states calculations and experimental data.
• Vibrational density of states indicate degradation of covalent bonds in HDA and show similarities to high-density liquid silicon.

Conclusions:

• The structural transformation from LDA to HDA silicon leads to significant changes in electronic and vibrational properties.
• Highly distorted tetrahedral configurations in HDA silicon are responsible for its enhanced metallic nature.
• The study provides insights into the phase transitions and properties of amorphous silicon under pressure.