Electronic States of Al–Mg–Zn Quasicrystal and Its Approximant Based on First‐Principles Calculations.

First‐principles calculations are performed to investigate the electronic states of 1/1 and 2/1 approximants with the composition Al15Zn40Mg45, which is close to the quasicrystal (QC) Al14.9Zn41.0Mg44.1 in which the superconductivity recently has been discovered. The density of states for the 1/1 approximant shows a wide pseudogap structure near the Fermi level as commonly observed in various approximants of the QCs, whereas those for the 2/1 approximant do not show such a wide pseudogap. Instead of the wide pseudogap, the 2/1 approximant shows a remarkable narrow pseudogap at the Fermi level in contrast to the 1/1 approximant, which shows a shallow hump at the Fermi level within the wide pseudogap. This seems to be consistent with the experimental observation of the electrical resistivity, which increases with decreasing temperature from room temperature down to around the superconducting transition temperature for the 2/1 approximant together with the QC, whereas it monotonically decreases for the 1/1 approximant. [ABSTRACT FROM AUTHOR]