Effects of surface structure and halogen substitution on electronic charge transfer in adlayers of (BETS)2-GaCl4 on silver surfaces

Results of DFT calculations are presented that focus on changes to charge transfer, energetics, and geometry in adlayers of (BETS)(2)-GaCl4 (an organic superconductor Bechgaard salt, 'OSC') as modulated by changes in surface and degree of substitution to its halogens. Specifically, results are presented for the charge transfer to/in adlayers of lambda-(BETS)(2)-GaCl4 on the Ag(111) and Ag(100) surfaces; and on both surfaces including further the effects of multiple successive F substitutions for Cl onto the Ga center. Results show two interesting important phenomena: first, that the amount of charge transfer is indeed highly surface sensitive (by about 0.5 net electron in this case), and second, that substitution of different amounts of F atoms on the Ga center also has profound effects on the charge transfer to the Ga atom in the GaCl(4-x)Fx center, albeit in nonlinear and counterintuitive ways which essentially conserve total net charge in the overall adlayer. The results of this work, in summary, provide insight which should help understand the degree to which surface-mediated modulation of assembled adlayers of nanoelectronic materials and their electronic structure can be varied and further supplements recent work on superhalogenated OSC charge transfer materials.