Although the beryllium-tungsten phase diagram has been well known for many years, several experiments indicate that alloy formation, after annealing and diffusion of beryllium from a film deposited on a tungsten substrate, is more difficult than the reverse process; this point is of great importance in various domains, such as nuclear fusion devices. Beside this applications-oriented aspect, our Letter approaches a more fundamental point of view through quantum modeling of the surface reactivity and metals alloying starting from surface processes. The study is lead through density functional theory (DFT) calculation, and projected electron density of states (DOS) involved. (C) 2009 Elsevier B.V. All rights reserved.