• MOJTABA YAGHOBI

      Articles written in Pramana – Journal of Physics

    • Effect of doping of N and B atoms on thermoelectric properties of C60 molecule

      Mojtaba Yaghobi Fazel Ardeshir Larijani

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      In this work, the doping effect on the thermoelectric properties of the C60 molecule (fullerene) was studied by considering inelastic electron–phonon interactions. It is seen that the maximum value of thermal conductance (𝑘max) with respect to the molecules are 𝑘max(C59N) < 𝑘max(C60) < 𝑘max(C59B). Also, the oscillatory behaviour of thermal conductance is dramatically dependent on the type of molecules. The values of figure of merit (ZT) against energy and with respect to the type of molecules are between 0.25 × 10−5 and 0.194 × 10−3 and effect of the type of molecules is small on the minimum value of ZT.

    • Structural and optical properties of the M@C59X cages (X=N, B and M=Li, Na)

      Mojtaba Yaghobi Alireza Adabinezhad

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      Using B3LYP/6-31G* density functional level of theory, the structural and optical properties of the C60 and M@C59X cages have been investigated. Results indicate that the charge on C atoms and band gap of C60 cage are changed dramatically with the substitution of one B or N atom at one of the C sites and the Li and Na atom encapsulations in the C60 cage. The Mulliken analyses show that the charge is transferred completely between the alkali atoms and the C59X cage. The substitutional and encapsulation doping (SED) reduce the optical gaps of the C60 cage. Also, the oscillator strengths of the absorption peaks are dependent on dopant types.

    • Tunnel magnetoresistance in the $B_{n}N_{n}(n = 12, 24)$ cages

      YAGHOOB MOHAMMADMORADI MOJTABA YAGHOBI

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      In this study, the effects of the type of the cage, the bias and gate voltages on spin transport properties of electrons in magnetic tunnel junction (MTJ) of $B_{n}N_{n}(n = 12, 24)$ cages were investigated by theoretical methods. For a gate voltage $(V_{g})$ more than 0.5V, the device became electrically conductive at $V_{b} = 0.5 V$. The electric current increased linearly for bias voltages more than $|V_{b}|$ = 1 V at $V_{g}$ = 0.0 V. The maximum value of the tunnel magnetic resistance (TMR) ratio was $\sim 75%$ for $\rm{B_{12}N_{12}}$ and 60% for $\rm{B_{24}N_{24}}$ molecules. The maximum values of TMR against the bias voltage $(V_{b})$ were seen at 1.6V (−1.6V) for $\rm{B_{12}N_{12}}$ and 0.0V for $\rm{B_{24}N_{24}}$. At $V_{b}$ = 0.5 V, the TMR ratio was changed by varying the gate voltage. Finally, the spin transport properties of the $\rm{B_{12}N_{12}}$ cage were compared with those of the $\rm{B_{24}N_{24}}$ and $\rm{C_{60}}$ cages.

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