EFFECT OF ORTHORHOMBIC DISTORTION AND 2ND-NEAREST NEIGHBOR HOPPING ONGAP-TO-T-C RATIO

Within the framework of the BCS theory, we perform a numerical study o f the effect of orthorhombic distortion and second nearest neighbor ho pping on the ratio R = 2 Delta(0)/T-c based on the van Hove singularit y scenario. We find that the gap-to-T-c ratio depends on the distortio n and hopping parameters, in contradiction to the recent conclusion of Sarkar et al. [Phys. Rev. B 51, 12854 (1995)]. In particular, the int roduction of orthorhombic distortion increases the value of R, and wit h decreasing second neighbor hopping, R decreases.