4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

A Mixed Basis Density Functional Approach For Low Dimensional Carbon-based Systems With B-splines

The electronic properties of low-dimensional systems are fundamentally different from those in higher dimensions due to their unusual collective excitations. Nowadays, 1-dimensional (1D) or 2-dimensional (2D) materials can be easily fabricated due to the emerging nanotechnology, which leads to intensive exploration of low-dimensional systems for material innovation Here, a mixed basis approach based on density functional theory is employed to study 1D and 2D carbon-related systems [1,2]. The basis functions are taken to be the localized B-splines for the finite non-periodic dimension(s) and the plane waves for the periodic directions. The use of this mixed basis has several advantages over the supercell modeling: (1) It resumes the layer-like local geometry which appears in surfaces and describes the wavefunction in a natural way. (2) Because one can calculate the total energy for an isolated system instead of using a supercell consisting of alternating slab and vacuum regions, the physical quantity, such as the work function can be immediately obtained without any correction. (3) For charged systems, the spurious Coulomb interaction between the defect, its images and the compensating background charge in the supercell approach can be automatically avoided.(4) The number of the basis is significantly reduced, easing the computational burden for the diagonalization of the Kohn-Sham Hamiltonian. To test the present method, we apply it to study the C(001)-(2×1) surface, n-type δ-doped graphene, infinite carbon-dimer chain, graphene nanoribbon, carbon nanotube and positively-charged carbon-dimer chain and graphene. The Van der Waals interaction for graphite is also taken into account. The resulting electronic structures are presented and discussed in detail.
Keywords: mixed basis, density functional theory, low-dimensional system
Chung-Yuan Ren, Yia-Chung Chang, Chen-Shiung Hsue