Twin boundary energy and characterization of charge redistribution near the twin boundaries of cupperate superconductors

• Ab initio simulation for twin boundary energy in YBCO system for the 1st time.
• Study of the twin boundary energy variation versus the inserted strain.
• Proportionality of twin lamella width by the inserted strain.
• Local charge transfer and charge redistribution on the twin planes.
• Total DOSs for the twined system at Fermi level is higher than the untwined one.
• This explain the effect of twin boundaries in agreement with experimental data.

Ab-initio calculations under general gradient approximation have been employed for the first time to find out twin boundary energy, γ, in twined YBCO systems. Despite a vast discrepancy in reported experimental values, our results show that the γ value falls in the range of 40–85 mJ/m2. On the other hand, functional form of γ versus inserted strains shows that the mean value for the twin width lamella would tend to approach zero as the strain goes to zero. We have also investigated the local charge transfer and the modification of the electronic states of the basal and twin planes in YBCO, because the charge redistribution at interfaces can modify transport across the grains considerably and determine the applicability of high-Tc superconductors in the electronic applications. The total density of electronic states at the Fermi level for the twined system is enhanced in comparison with the untwined one. Our results explain the influence of twin boundaries in superconductive properties of YBCO, in experimental situations.