Density functional theory- (DFT-) based ab initio calculations were used to investigate the surface-to-surface interaction and\r\nfrictional behavior of two hydrogenated C(100) dimer surfaces. A monolayer of hydrogen atoms was applied to the fully relaxed\r\nC(100)2x1 surface having rows of C=C dimers with a bond length of 1.39 Ã?° A. The obtained C(100)2x1-H surfaces (Cââ?¬â??H bond length\r\n1.15 Ã?° A) were placed in a large vacuum space and translated toward each other. A cohesive state at a surface separation of 4.32 Ã?°A that\r\nis stabilized by approximately 0.42 eV was observed. An increase in the charge separation in the surface dimer was calculated at\r\nthis separation having a 0.04 e transfer from the hydrogen atom to the carbon atom.TheMayer bond orders were calculated for the\r\nCââ?¬â??C and Cââ?¬â??H bonds and were found to be 0.962 and 0.947, respectively. ?? Cââ?¬â??H bonds did not change substantially from the fully\r\nseparated state. A significant decrease in the electron density difference between the hydrogen atoms on opposite surfaces was seen\r\nand assigned to the effects of Pauli repulsion. The surfaces were translated relative to each other in the (100) plane, and the friction\r\nforce was obtained as a function of slab spacing, which yielded a 0.157 coefficient of friction.
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