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Tuning the electronic properties of boron nitride nanotube by mechanical uni-axial deformation: a DFT study.

Ju SP, Wang YC, Lien TW - Nanoscale Res Lett (2011)

Bottom Line: The effect of uni-axial strain on the electronic properties of (8,0) zigzag and (5,5) armchair boron nitride nanotubes (BNNT) is addressed by density functional theory calculation.The stress-strain profiles indicate that these two BNNTS of differing types display very similar mechanical properties, but there are variations in HOMO-LUMO gaps at different strains, indicating that the electronic properties of BNNTs not only depend on uni-axial strain, but on BNNT type.The variations in nanotube geometries, partial density of states of B and N atoms, B and N charges are also discussed for (8,0) and (5,5) BNNTs at different strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Electro-Mechanical Engineering, Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Kaohsiung, 804, Taiwan. jushin-pon@mail.nsysu.edu.tw.

ABSTRACT
The effect of uni-axial strain on the electronic properties of (8,0) zigzag and (5,5) armchair boron nitride nanotubes (BNNT) is addressed by density functional theory calculation. The stress-strain profiles indicate that these two BNNTS of differing types display very similar mechanical properties, but there are variations in HOMO-LUMO gaps at different strains, indicating that the electronic properties of BNNTs not only depend on uni-axial strain, but on BNNT type. The variations in nanotube geometries, partial density of states of B and N atoms, B and N charges are also discussed for (8,0) and (5,5) BNNTs at different strains.

No MeSH data available.


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PDOS profiles of B63 and N61 atoms.
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Figure 8: PDOS profiles of B63 and N61 atoms.

Mentions: The partial density of states (PDOS) profiles for B68 and N35 atoms of the (8,0) BNNT and for B63 and N61 atoms of the (5,5) BNNT, as shown in Figures 7 and 8, respectively, are further studied to demonstrate the strain effect on the electronic structures of BNNTs. Figure 7a,b,c,d,e shows the PDOS of s and p orbitals of B68 and N35 atoms as well as the summation of these orbitals for the (8,0) BNNT. At strain of 0, there is no contribution to the total DOS from B68 2s and N35 2s orbitals around the Fermi level. It should be noted that the total DOS strength of empty states near Fermi level mainly comes from N35 2p electron and to a lesser degree B68 2p electron. The N35 2p orbital contributes more to the total DOS of occupied states near the Fermi level, and grabs electron from nearby B atoms. Moreover, the LUMO mainly comes from the B68 2p orbital and to a lesser degree N35's 2p orbital. Consequently, N atoms have negative charges and B atoms possess positive charges, which can be seen in Figure 6. At strain of 5%, the unoccupied state is split into two states, resulting in a significant decrease in the HOMO-LUMO gap when the strain is larger than 5%, as shown in Figure 2a. When the strain increases from 5 to 13%, the relative strengths of two split states become more dramatic, which can be seen in Figure 7b,c,d. At strain of 21%, both the occupied and unoccupied states display a significant left-shift and the two split unoccupied states merge into one unoccupied state, as shown in Figure 7e. The contribution from the B68 2p to the HOMO becomes less significant when the strain becomes larger, which can be seen at the peak indicated by arrows in Figure 7a,b,c,d,e. This reveals that N atoms will grab more electrons from B atoms when the strain becomes larger, and B and N atoms become more ionic, as was shown in Figure 6.


Tuning the electronic properties of boron nitride nanotube by mechanical uni-axial deformation: a DFT study.

Ju SP, Wang YC, Lien TW - Nanoscale Res Lett (2011)

PDOS profiles of B63 and N61 atoms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211212&req=5

Figure 8: PDOS profiles of B63 and N61 atoms.
Mentions: The partial density of states (PDOS) profiles for B68 and N35 atoms of the (8,0) BNNT and for B63 and N61 atoms of the (5,5) BNNT, as shown in Figures 7 and 8, respectively, are further studied to demonstrate the strain effect on the electronic structures of BNNTs. Figure 7a,b,c,d,e shows the PDOS of s and p orbitals of B68 and N35 atoms as well as the summation of these orbitals for the (8,0) BNNT. At strain of 0, there is no contribution to the total DOS from B68 2s and N35 2s orbitals around the Fermi level. It should be noted that the total DOS strength of empty states near Fermi level mainly comes from N35 2p electron and to a lesser degree B68 2p electron. The N35 2p orbital contributes more to the total DOS of occupied states near the Fermi level, and grabs electron from nearby B atoms. Moreover, the LUMO mainly comes from the B68 2p orbital and to a lesser degree N35's 2p orbital. Consequently, N atoms have negative charges and B atoms possess positive charges, which can be seen in Figure 6. At strain of 5%, the unoccupied state is split into two states, resulting in a significant decrease in the HOMO-LUMO gap when the strain is larger than 5%, as shown in Figure 2a. When the strain increases from 5 to 13%, the relative strengths of two split states become more dramatic, which can be seen in Figure 7b,c,d. At strain of 21%, both the occupied and unoccupied states display a significant left-shift and the two split unoccupied states merge into one unoccupied state, as shown in Figure 7e. The contribution from the B68 2p to the HOMO becomes less significant when the strain becomes larger, which can be seen at the peak indicated by arrows in Figure 7a,b,c,d,e. This reveals that N atoms will grab more electrons from B atoms when the strain becomes larger, and B and N atoms become more ionic, as was shown in Figure 6.

Bottom Line: The effect of uni-axial strain on the electronic properties of (8,0) zigzag and (5,5) armchair boron nitride nanotubes (BNNT) is addressed by density functional theory calculation.The stress-strain profiles indicate that these two BNNTS of differing types display very similar mechanical properties, but there are variations in HOMO-LUMO gaps at different strains, indicating that the electronic properties of BNNTs not only depend on uni-axial strain, but on BNNT type.The variations in nanotube geometries, partial density of states of B and N atoms, B and N charges are also discussed for (8,0) and (5,5) BNNTs at different strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical and Electro-Mechanical Engineering, Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Kaohsiung, 804, Taiwan. jushin-pon@mail.nsysu.edu.tw.

ABSTRACT
The effect of uni-axial strain on the electronic properties of (8,0) zigzag and (5,5) armchair boron nitride nanotubes (BNNT) is addressed by density functional theory calculation. The stress-strain profiles indicate that these two BNNTS of differing types display very similar mechanical properties, but there are variations in HOMO-LUMO gaps at different strains, indicating that the electronic properties of BNNTs not only depend on uni-axial strain, but on BNNT type. The variations in nanotube geometries, partial density of states of B and N atoms, B and N charges are also discussed for (8,0) and (5,5) BNNTs at different strains.

No MeSH data available.


Related in: MedlinePlus