Understanding the physical properties of heterogeneous integration, such as the epitaxial growth of III-V on Si, is highly desirable for more advanced and futuristic optoelectronic and photoelectric applications of semiconductors [1, 2]. Using density functional theory, we first demonstrate how it is possible to investigate the absolute surface and interface energies with the variations of chemical potential for heterogeneous materials systems [3, 4]. Then, we show how to quantify the impact of Si surface passivation before III-V/Si hetero-epitaxy on the surface energy of the Si initial substrate, which plays an essential role in establishing its wetting characteristics on the specific case of GaP/Si [5]. In addition, we highlight that this inevitable passivation leads to a considerable reduction of the substrate surface energy, which in turn leads to a significant decrease in spreading parameters and evidence the heteroepitaxy in 3D Volmer-Weber type. Finally, we explore the possibilities to have a full ab initio description of Wulff-Kaishew equilibrium morphology prediction. [1] I. Lucci, S. Charbonnier, M. Vallet, P. Turban, Y. Léger, T. Rohel, N. Bertru, A. Létoublon, J. Rodriguez, L. Cerutti, E. Tournié, A. Ponchet, G. Patriarche, L. Pedesseau, and C. Cornet, Adv Funct Materials 28(30), 1801585 (2018). [2] C. Cornet, S. Charbonnier, I. Lucci, L. Chen, A. Létoublon, A. Alvarez, K. Tavernier, T. Rohel, R. Bernard, J.-B. Rodriguez, L. Cerutti, E. Tournié, Y. Léger, M. Bahri, G. Patriarche, L. Largeau, A. Ponchet, P. Turban, and N. Bertru, Phys. Rev. Materials 4(5), 053401 (2020). [3] I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Létoublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet, Phys. Rev. Materials 2(6), 060401(R) (2018). [4] S. Pallikkara Chandrasekharan, I. Lucci, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 108(7), 075305 (2023). [5] S. Pallikkara Chandrasekharan, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 109(4), 045304 (2024).