Adatom Interactions on GaN(0001) Surface I: Coverage-Dependent Adsorption

Abstract

The adsorption of an adatom on the surface of a crystal is affected by the surface coverage due to adatom–adatom and adatom–substrate interactions. We study the dependence of adsorption energy of Ga and N adatoms on wurtzite GaN(0001) as a function of decreasing surface coverage from 0.25 to 0.04 monolayers through first-principles calculations. The adsorption energies of Ga and N adatoms on the flat, clean GaN(0001) substrate do not converge with decreasing coverage. Further, it appears that the Ga and N adatoms significantly distort the substrate lattice from the flat configuration. We found that these distortions increase with increase in system size (or, equivalently, with reducing coverage). This observation is counterintuitive since it is expected that lattice distortions should decrease with decreasing surface coverage. We separate the different contributions to the adsorption energy and identify the part of adsorption energy that arises due to lattice distortions. This contribution appears to be much larger than the contribution due to dipolar interaction between adatoms and their periodic images. This also allows us to identify some surface reconstructions of clean GaN(0001) that have not been reported yet, which are lower in energy than the flat clean substrate. The adsorption energies calculated with respect to these reconstructed configurations converge with increasing system size. This size-dependent or coverage-dependent study suggests that the effect of lattice distortions should be carefully taken into account when calculating adsorption energy for periodic systems from first-principles methods.

Reaction Pathway of Surface-Catalyzed Ammonia Decomposition and Nitrogen Incorporation in Epitaxial Growth of Gallium Nitride

“…The H3 site provides smaller but comparable binding energy while the T1 site does much smaller binding energy. Previous density functional calculations have also shown that the T4 site is most energetically favorable for a Ga adatom. , When we count the number of Ga dangling bonds in the 2 × 2 lateral cell, it is four on the bare surface. When a Ga adatom is adsorbed on either T4 or H3 site, the number of the Ga dangling bond becomes two.…”

Statistical Mechanics in Theoretical Chemistry in India : Past, present and a bit of future

“…See, for example, Refs. (Das and Paul, 2017;Chand et al, 2018;Dasari and Mallik, 2018;Kaur and Kashyap, 2018;Awasthi et al, 2016;Awasthi and Nair, 2017;Awasthi et al, 2018;Chugh and Ranganathan, 2016;Ghosh and Ranganathan, 2017;Chugh and Ranganathan, 2017;Sarkar et al, 2019;Maity and Reddy, 2018;Nandi et al, 2017;Hridya and Mukherjee, 2018;Sharma and Ghorai, 2018;Ahalawat and Murarka, 2017;Rout and Srinivasan, 2018;Shekar and Swathi, 2018;Kumawat and Chakrabarty, 2017;Palchowdhury and Bhargava, 2018;Mandal et al, 2018;Ahalawat and Mondal, 2018;Hasnain and Bandyopadhyay, 2015;Dutta and Nandi, 2015) for representative work from these groups in recent years. Also, many institutes now have multiple research groups working in statistical mechanics and computer simulations.…”

“…Also, many institutes now have multiple research groups working in statistical mechanics and computer simulations. For example, at IIT Kanpur, the groups of Ranganathan and Nair are involved, respectively, in studies of surface growth and rare events using advanced simulation methods of kinetic Monte Carlo and metadynamics (Awasthi et al, 2016;Awasthi and Nair, 2017;Awasthi et al, 2018;Chugh and Ranganathan, 2016;Ghosh and Ranganathan, 2017;Chugh and Ranganathan, 2017). These groups are also actively involved in methodological developments of computer simulations using advanced theoretical techniques and computer tools.…”

Электронная структура наноинтерфейса Cs/n-GaN(0001)

“…Существует ряд расчетов адсорбции Cs на GaN [10,11,16,17]. При адсорбции Cs на n-GaN(0001)-2 × 2 показано, что при покрытиях 0.33 монослоя (ML) происходит формирование зоны около E F , образованной при гибридизации орбиталей Cs 6s, Cs 5p и Ga 4p [10] Адсорбция Cs в субмонослойном режиме на n-GaN(0001) не вызывает существенных изменений в спектрах фотоэмиссии.…”