First-principles density functional theory (DFT) calculations were performed to investigate the l... more First-principles density functional theory (DFT) calculations were performed to investigate the lithium (Li) adsorption upon beryllium (Be) doped graphene. Be acts as hole doping in graphene leaving the structure as electron deficient, offering a greater tendency for Li adsorption than in pristine and boron (B) doped graphene. The introduction of Be augments the adsorption energy of Li from −1.11 to −2.53 eV/Li. Furthermore, 12, and 16 Li ions can easily be captured by one Be center in the single and double vacancy case, respectively, with the adsorption energies of −1.33 eV/Li (for both the cases), showing that Be doped graphene is an excellent anode material for lithium ion batteries (LIBs). Consequently, the presence of structural defects, in particular, a divacancy is found to be more efficient in terms of Li storage capacity. A huge Li storage capacity (2303.295 mAh/g) is calculated for Li 8 BeC 7 having reasonable adsorption energy (−1.47 eV/Li). Our calculated capacity is 6.19 times greater than that of the graphite.
The structure, stability, electronic properties and chemical reactivity
of X/B/N triple-doped gra... more The structure, stability, electronic properties and chemical reactivity of X/B/N triple-doped graphene (TDG) systems (X=Al, Si, P, S) are investigated by means of periodic density functional calculations. In the studied TDGs the dopant atoms prefer to be bonded to one another instead of separated. In general, the XNB pattern is preferred, with the exception of sulfur, which favors the SBN motif. The introduction of a third dopant results in a negligible decrease of the cohesive energies with respect to the dual-doped graphene (DDG) counterparts. Thus, it is expect that these systems can be prepared soon. For SiNB TDG, the introduction of the B dopant reduces the gap opening at the K point and restores the Dirac cones that are destroyed in SiN DDG. On the contrary, for PNB TDG, the bandgap is increased with respect to PN DDG, probably because the introduction of B weakens the PN bonding, and thus the electronic structure is rather similar to that of P-doped graphene. Finally, with regard to the reactivity of the TDGs, for AlNB, PNB, and SNB the carbon atoms are more reactive than in their AlN, PN, and SN DDG counterparts. On the contrary, the reactivity of SiNB is lower than that of SiN DDG. Therefore, to increase the reactivity of graphene, Al, P, and S should be combined with BN motifs.
Herein, we performed ab initio calculations to study the structural strain in graphene by non-pla... more Herein, we performed ab initio calculations to study the structural strain in graphene by non-planar substitution of a polar BeO molecule and analyzed its effect on electronic and magnetic structures. Two modes of doping, i.e., Be within graphene plane (replaced with C atom) with O upright (outside the plane) and vice versa, were investigated in both spin-polarized and non-spin-polarized modes. The resultant strain demolished the sp 2 hybridization, leading to some interesting effects in the electronic structure. A significant distortion in the structures of the system was realized. It is observed that such a structure distortion causes the induction of energy gaps of varying nature (direct as well as indirect). The highest value of band gap (0.44 eV) is observed in the case where the O atom of the BeO molecule remains drilled through the graphene structure. It is observed that despite the dopant being polar, spin-polarized calculations do not give remarkably different results relative to their non-spin polarized counterpart as no magnetic moment was recorded after inducing spin-polarization. In addition, bonding mechanisms have been discussed for all the cases elaborating significant variations with changes in the BeO orientation as well as the nature of calculations. The amount of band-gap that varies between 0.31 to 0.44 eV is suitable for employing such systems in the manufacturing of field effect transistors. Moreover, the results indicate the possibility of using these systems in the vast field of nano-electronic and spintronic devices. Increasing the supercell size reduces the band gap due to a decrease in concentration.
First-principles density functional theory (DFT) calculations were carried out to investigate the... more First-principles density functional theory (DFT) calculations were carried out to investigate the rectangular and hexagonal doping of graphene with B, N, and O. In both of these configurations, though the dopants are incorporated at the same sublattices sites (A or B), the calculated values of the band gaps are very different with nearly the same amount of cohesive energies. In this study, the highest value of the band gap (1.68 eV) is achieved when a maximum of 4 O atoms are substituted at hexagonal positions, resulting in a lower cohesive energy relative to that of the other studied systems. Hexagonal doping with 3 O atoms is significantly more efficient in terms of opening the band gap and improving the structural stability than the rectangular doping with 4 O atoms. Our results show the opportunity to induce a higher band gap values having a smaller concentration of dopants, with better structural stabilities.
First-principles density functional theory (DFT) based calculations were carried out to investiga... more First-principles density functional theory (DFT) based calculations were carried out to investigate the structural and electronic properties of beryllium and nitrogen co-doped and BeN/BeO molecules-doped graphene systems. The basic focus was on how the band-gap could be fine-tuned with concentration and replacement/site(s) variations. It was interesting to note that the increase in doping concentration of this hetero combination of electrons (N) and holes (Be) into the graphene systems did not always lead to a higher band-gap. The insertion of holes and electrons at hetero sites, simultaneously, leads to an increase in the energy-gap. However, if the replacement combination of sites comprises of the same rectangular, or hexagonal, ones, then the band-gap may decrease with increasing impurity concentrations. Additionally, the insertion of BeO molecule(s) was also position dependent and the band-gap enhancement was not always proportional to the density of doped BeO molecules. Finally, our results suggested that with control of the dopant position, very fine-tuning of the band-gap is possible. This makes graphene a favorable material for utilization in diverse electronic device applications.
First-principles density functional theory (DFT) calculations were carried out to investigate the... more First-principles density functional theory (DFT) calculations were carried out to investigate the structural and electronic properties of beryllium (Be) doped and Be and boron (B) co-doped graphene systems. We observed that not only the concentration of impurity atoms is important to tune the band-gap to some desired level, but also the specific substitution sites play a key role. In our system, which consists of 32 atoms, a maximum of 4Be and, in the co-doped state, 2Be and 3B atom substitutions are investigated. Both dopants are electron deficient relative to C atoms and cause the Fermi level to shift downward (p-type doping). A maximum band gap of 1.44 eV can be achieved on incorporation of 4Be atoms. The introduction of Be is more sensitive in terms of geometry and stability than B. However, in opening the energy gap, Be is more effective than B and N (nitrogen). Our results offer the possibility to modify the band-gap of graphene sufficiently for utilization in diverse electronic device applications.
First-principles density functional theory (DFT) calculations were performed to investigate the l... more First-principles density functional theory (DFT) calculations were performed to investigate the lithium (Li) adsorption upon beryllium (Be) doped graphene. Be acts as hole doping in graphene leaving the structure as electron deficient, offering a greater tendency for Li adsorption than in pristine and boron (B) doped graphene. The introduction of Be augments the adsorption energy of Li from −1.11 to −2.53 eV/Li. Furthermore, 12, and 16 Li ions can easily be captured by one Be center in the single and double vacancy case, respectively, with the adsorption energies of −1.33 eV/Li (for both the cases), showing that Be doped graphene is an excellent anode material for lithium ion batteries (LIBs). Consequently, the presence of structural defects, in particular, a divacancy is found to be more efficient in terms of Li storage capacity. A huge Li storage capacity (2303.295 mAh/g) is calculated for Li 8 BeC 7 having reasonable adsorption energy (−1.47 eV/Li). Our calculated capacity is 6.19 times greater than that of the graphite.
The structure, stability, electronic properties and chemical reactivity
of X/B/N triple-doped gra... more The structure, stability, electronic properties and chemical reactivity of X/B/N triple-doped graphene (TDG) systems (X=Al, Si, P, S) are investigated by means of periodic density functional calculations. In the studied TDGs the dopant atoms prefer to be bonded to one another instead of separated. In general, the XNB pattern is preferred, with the exception of sulfur, which favors the SBN motif. The introduction of a third dopant results in a negligible decrease of the cohesive energies with respect to the dual-doped graphene (DDG) counterparts. Thus, it is expect that these systems can be prepared soon. For SiNB TDG, the introduction of the B dopant reduces the gap opening at the K point and restores the Dirac cones that are destroyed in SiN DDG. On the contrary, for PNB TDG, the bandgap is increased with respect to PN DDG, probably because the introduction of B weakens the PN bonding, and thus the electronic structure is rather similar to that of P-doped graphene. Finally, with regard to the reactivity of the TDGs, for AlNB, PNB, and SNB the carbon atoms are more reactive than in their AlN, PN, and SN DDG counterparts. On the contrary, the reactivity of SiNB is lower than that of SiN DDG. Therefore, to increase the reactivity of graphene, Al, P, and S should be combined with BN motifs.
Herein, we performed ab initio calculations to study the structural strain in graphene by non-pla... more Herein, we performed ab initio calculations to study the structural strain in graphene by non-planar substitution of a polar BeO molecule and analyzed its effect on electronic and magnetic structures. Two modes of doping, i.e., Be within graphene plane (replaced with C atom) with O upright (outside the plane) and vice versa, were investigated in both spin-polarized and non-spin-polarized modes. The resultant strain demolished the sp 2 hybridization, leading to some interesting effects in the electronic structure. A significant distortion in the structures of the system was realized. It is observed that such a structure distortion causes the induction of energy gaps of varying nature (direct as well as indirect). The highest value of band gap (0.44 eV) is observed in the case where the O atom of the BeO molecule remains drilled through the graphene structure. It is observed that despite the dopant being polar, spin-polarized calculations do not give remarkably different results relative to their non-spin polarized counterpart as no magnetic moment was recorded after inducing spin-polarization. In addition, bonding mechanisms have been discussed for all the cases elaborating significant variations with changes in the BeO orientation as well as the nature of calculations. The amount of band-gap that varies between 0.31 to 0.44 eV is suitable for employing such systems in the manufacturing of field effect transistors. Moreover, the results indicate the possibility of using these systems in the vast field of nano-electronic and spintronic devices. Increasing the supercell size reduces the band gap due to a decrease in concentration.
First-principles density functional theory (DFT) calculations were carried out to investigate the... more First-principles density functional theory (DFT) calculations were carried out to investigate the rectangular and hexagonal doping of graphene with B, N, and O. In both of these configurations, though the dopants are incorporated at the same sublattices sites (A or B), the calculated values of the band gaps are very different with nearly the same amount of cohesive energies. In this study, the highest value of the band gap (1.68 eV) is achieved when a maximum of 4 O atoms are substituted at hexagonal positions, resulting in a lower cohesive energy relative to that of the other studied systems. Hexagonal doping with 3 O atoms is significantly more efficient in terms of opening the band gap and improving the structural stability than the rectangular doping with 4 O atoms. Our results show the opportunity to induce a higher band gap values having a smaller concentration of dopants, with better structural stabilities.
First-principles density functional theory (DFT) based calculations were carried out to investiga... more First-principles density functional theory (DFT) based calculations were carried out to investigate the structural and electronic properties of beryllium and nitrogen co-doped and BeN/BeO molecules-doped graphene systems. The basic focus was on how the band-gap could be fine-tuned with concentration and replacement/site(s) variations. It was interesting to note that the increase in doping concentration of this hetero combination of electrons (N) and holes (Be) into the graphene systems did not always lead to a higher band-gap. The insertion of holes and electrons at hetero sites, simultaneously, leads to an increase in the energy-gap. However, if the replacement combination of sites comprises of the same rectangular, or hexagonal, ones, then the band-gap may decrease with increasing impurity concentrations. Additionally, the insertion of BeO molecule(s) was also position dependent and the band-gap enhancement was not always proportional to the density of doped BeO molecules. Finally, our results suggested that with control of the dopant position, very fine-tuning of the band-gap is possible. This makes graphene a favorable material for utilization in diverse electronic device applications.
First-principles density functional theory (DFT) calculations were carried out to investigate the... more First-principles density functional theory (DFT) calculations were carried out to investigate the structural and electronic properties of beryllium (Be) doped and Be and boron (B) co-doped graphene systems. We observed that not only the concentration of impurity atoms is important to tune the band-gap to some desired level, but also the specific substitution sites play a key role. In our system, which consists of 32 atoms, a maximum of 4Be and, in the co-doped state, 2Be and 3B atom substitutions are investigated. Both dopants are electron deficient relative to C atoms and cause the Fermi level to shift downward (p-type doping). A maximum band gap of 1.44 eV can be achieved on incorporation of 4Be atoms. The introduction of Be is more sensitive in terms of geometry and stability than B. However, in opening the energy gap, Be is more effective than B and N (nitrogen). Our results offer the possibility to modify the band-gap of graphene sufficiently for utilization in diverse electronic device applications.
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Papers by Saif Ullah
of X/B/N triple-doped graphene (TDG) systems (X=Al, Si,
P, S) are investigated by means of periodic density functional
calculations. In the studied TDGs the dopant atoms prefer to
be bonded to one another instead of separated. In general,
the XNB pattern is preferred, with the exception of sulfur,
which favors the SBN motif. The introduction of a third dopant
results in a negligible decrease of the cohesive energies with
respect to the dual-doped graphene (DDG) counterparts. Thus,
it is expect that these systems can be prepared soon. For SiNB
TDG, the introduction of the B dopant reduces the gap opening
at the K point and restores the Dirac cones that are destroyed
in SiN DDG. On the contrary, for PNB TDG, the bandgap
is increased with respect to PN DDG, probably because
the introduction of B weakens the PN bonding, and thus the
electronic structure is rather similar to that of P-doped graphene.
Finally, with regard to the reactivity of the TDGs, for
AlNB, PNB, and SNB the carbon atoms are more reactive than
in their AlN, PN, and SN DDG counterparts. On the contrary,
the reactivity of SiNB is lower than that of SiN DDG. Therefore,
to increase the reactivity of graphene, Al, P, and S should be
combined with BN motifs.
and electronic properties of beryllium (Be) doped and Be and boron (B) co-doped graphene systems. We
observed that not only the concentration of impurity atoms is important to tune the band-gap to some
desired level, but also the specific substitution sites play a key role. In our system, which consists of
32 atoms, a maximum of 4Be and, in the co-doped state, 2Be and 3B atom substitutions are
investigated. Both dopants are electron deficient relative to C atoms and cause the Fermi level to shift
downward (p-type doping). A maximum band gap of 1.44 eV can be achieved on incorporation of 4Be
atoms. The introduction of Be is more sensitive in terms of geometry and stability than B. However, in
opening the energy gap, Be is more effective than B and N (nitrogen). Our results offer the possibility to
modify the band-gap of graphene sufficiently for utilization in diverse electronic device applications.
of X/B/N triple-doped graphene (TDG) systems (X=Al, Si,
P, S) are investigated by means of periodic density functional
calculations. In the studied TDGs the dopant atoms prefer to
be bonded to one another instead of separated. In general,
the XNB pattern is preferred, with the exception of sulfur,
which favors the SBN motif. The introduction of a third dopant
results in a negligible decrease of the cohesive energies with
respect to the dual-doped graphene (DDG) counterparts. Thus,
it is expect that these systems can be prepared soon. For SiNB
TDG, the introduction of the B dopant reduces the gap opening
at the K point and restores the Dirac cones that are destroyed
in SiN DDG. On the contrary, for PNB TDG, the bandgap
is increased with respect to PN DDG, probably because
the introduction of B weakens the PN bonding, and thus the
electronic structure is rather similar to that of P-doped graphene.
Finally, with regard to the reactivity of the TDGs, for
AlNB, PNB, and SNB the carbon atoms are more reactive than
in their AlN, PN, and SN DDG counterparts. On the contrary,
the reactivity of SiNB is lower than that of SiN DDG. Therefore,
to increase the reactivity of graphene, Al, P, and S should be
combined with BN motifs.
and electronic properties of beryllium (Be) doped and Be and boron (B) co-doped graphene systems. We
observed that not only the concentration of impurity atoms is important to tune the band-gap to some
desired level, but also the specific substitution sites play a key role. In our system, which consists of
32 atoms, a maximum of 4Be and, in the co-doped state, 2Be and 3B atom substitutions are
investigated. Both dopants are electron deficient relative to C atoms and cause the Fermi level to shift
downward (p-type doping). A maximum band gap of 1.44 eV can be achieved on incorporation of 4Be
atoms. The introduction of Be is more sensitive in terms of geometry and stability than B. However, in
opening the energy gap, Be is more effective than B and N (nitrogen). Our results offer the possibility to
modify the band-gap of graphene sufficiently for utilization in diverse electronic device applications.