a Study of Buckminsterfullerene Using New Pseudopotentials.
Abstract
We present pseudopotential planewave localdensity calculations of the electronic and structural properties of solid C_{60} (fullerite). The calculated molecular bond lengths, lattice constant, bulk modulus, enthalpy of formation, and the equation of state for compression are in good agreement with experiment. The shape of the theoretical density of states is in excellent agreement with the experimental photoemission and inverse photoemission spectra. We also present the calculated bandstructure for the states near the fundamental gap. We have made a thorough analysis of the electronic states of C_{60} and found that they can be conveniently classified according to their angular character, and use it to identify the origin of the peaks in the electronic density of states. In order to perform accurate planewave converged C_{60} calculations, we have developed a simple procedure to generate firstprinciples normconserving pseudopotentials, which are designed to be smooth and therefore save computational resources when used with a planewave basis. We found that these pseudopotentials to be extremely efficient for cases where the planewave expansion has a slow convergence, in particular for systems containing first row elements such as carbon, transition metals and rareearth elements. The wide applicability of the pseudopotentials are exemplified with planewave calculations for copper, zincblende, diamond, alphaquartz, rutile and cerium. The large number of atoms in the C_ {60} system, imposes a heavy computational load on both storage and cpu time requirements. Therefore, we have investigated the computational requirements for the pseudopotential planewave method as a function of the number of atoms per unit cell. For systems containing a large number of atoms the computational load can be reduced if the pseudopotential operator is of a suitable form, such that it can be efficiently calculated in the position representation. The pseudopotentials we have examined include local pseudopotentials, position dependent electron mass pseudopotentials, and separable nonlocal pseudopotentials.
 Publication:

Ph.D. Thesis
 Pub Date:
 1991
 Bibcode:
 1991PhDT........93T
 Keywords:

 Engineering: Materials Science; Physics: Condensed Matter