Ab initio calculations on interaction of a C atom on small Ptn clusters (n = 1-10) show strong carbidic bonding and a decrease in the magnetic moments of Pt clusters. The adsorption energy decreases in an oscillatory way with increasing size but suggests no graphitic phase on small Pt clusters. Ptn clusters (n < 7) remain nearly planar after C adsorption but larger clusters have 3D structure. Further calculations of infrared and Raman spectra are reported. Interaction of H on pure and PtnC clusters shows stronger binding of H on PtnC clusters suggesting their better reactivity. © 2013 Elsevier B.V. All rights reserved.