The total energies of the bulk and slab alloys were obtained by performing density functional theory calculations with the plane wave-based Vienna ab initio simulation package (VASP) code (version 6.4.2). We employed the Perdew-Burke-Ernzerhof (PBE) functionals and the projector augmented wave (PAW) potentials to describe exchange-correlation interactions and the ionic cores, respectively. The electronic wave functions of the quasiparticles were expanded using a planewave basis set up to a cutoff energy of 300 eV, which is larger than the default values preset in the potentials for platinum, palladium, and silver. Dipole moment corrections were not necessary for the symmetric slabs because of the cancelation by the identical surfaces oriented in opposite directions.