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23. Ab initio and classical molecular dynamics simulations of N2 desorption from TiN(001) surfaces.

Author

Sangiovanni, D.G., Edström, D., Hultman, L., Petrov, I., Greene, J.E., and Chirita, V.

Subjects
*MOLECULAR dynamics, *TIN compounds, *DENSITY functional theory, *DESORPTION, *ADATOMS, *SURFACE diffusion, *MATERIALS science
Abstract

Ab initio molecular dynamics simulations based on density functional theory show that N adatoms are chemisorbed in threefold sites close to a N surface atom and between the two diagonally opposed neighboring Ti surface atoms on TiN(001). The most probable N adatom reaction pathway, even in the presence of nearby N adatoms, is for the N adatom and N surface atom pair to first undergo several exchange reactions and then desorb as a N2 molecule, resulting in a surface anion vacancy, with an activation barrier E des of 1.37eV and an attempt frequency A des =3.4×1013 s−1. E des is essentially equal to the N adatom surface diffusion barrier, Es =1.39eV, while As is only three to four times larger than A des, indicating that isolated N adatoms migrate for only short distances prior to N2 desorption. The probability of N2 desorption via recombination of N adatoms on TiN(001) is much lower due to repulsive adatom/adatom interactions at separations less than ~3Å which rapidly increase to ~2eV at a separation of 1.5Å. We obtain good qualitative and quantitative agreement with the above results using the modified embedded atom method potential to perform classical molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Published
2014
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