Quantum Monte Carlo methods for fermionic systems : beyond the fixed-node approximation

Download

index.pdf

Date

2010

Author

Dugan, Nazım

Metadata

Show full item record

Item Usage Stats

167
views

64
downloads

Developments are made on the quantum Monte Carlo methods towards increasing the precision and the stability of the non fixed-node projector calculations of fermions. In the first part of the developments, the wavefunction correction scheme, which was developed to increase the precision of the di usion Monte Carlo (DMC) method, is applied to non fixed-node DMC to increase the precision of such fermion calculations which do not have nodal error. The benchmark calculations indicate a significant decrease of statistical error due to the usage of the correction scheme in such non fixed-node calculations. The second part of the developments is about the modifications of the wavefunction correction scheme for having a stable non fixed-node DMC algorithm for fermions. The minus signed walkers of the non fixed-node calculations are avoided by these modifications in the developed stable algorithm. However, the accuracy of the method decreases, especially for larger systems, as a result of the discussed modifications to overcome the sign instability.

Subject Keywords

Monte Carlo method., Quantum theory., Condensed matter., Atomic physics.

URI

http://etd.lib.metu.edu.tr/upload/12612256/index.pdf
https://hdl.handle.net/11511/20019

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Nonlinear optical properties of semiconductor heterostructures Yıldırım, Hasan; Tomak, Mehmet; Department of Physics (2006) The nonlinear optical properties of semiconductor heterostructures, such as GaAsAl/GaAs alloys, are studied with analytic and numerical methods on the basis of quantum mechanics. Particularly, second and third-order nonlinear optical properties of quantum wells described by the various types of confining potentials are considered within the density matrix formalism. We consider a Pöschl-Teller type potential which has been rarely considered in this area. It has a tunable asymmetry parameter, making it a goo...
Adsorption of gold atoms on anatase TiO2 (100)-1x1 surface Vural, Kıvılcım Başak; Ellialtıoğlu, Süleyman Şinasi; Department of Physics (2009) In this work the electronic and structural properties of anatase TiO2 (100) surface and gold adsorption have been investigated by using the first-principles calculations based on density functional theory (DFT). TiO2 is a wide band-gap material and to this effects it finds numerous applications in technology such as, cleaning of water, self-cleaning, coating, solar cells and so on. Primarily, the relation between the surface energy of the anatase (100)-1x1 phase and the TiO2-layers is examined. After an app...
Hamiltonian for a particle in a magnetic field on a curved surface in orthogonal curvilinear coordinates Shikakhwa, M. S.; Chair, N. (2016-08-19) The Schrodinger Hamiltonian of a spin-less particle as well as the Pauli Hamiltonian with spin-orbit coupling included of a spin one-half particle in electromagnetic fields that are confined to a curved surface embedded in a three-dimensional space spanned by a general Orthogonal Curvilinear Coordinate are constructed. A new approach, based on the physical argument that upon squeezing the particle to the surface by a potential, then it is the physical gauge-covariant kinematical momentum operator (velocity ...
Electronic properties of open-ended single wall carbon nanotubes Turker, L; Erkoç, Şakir (2002-01-31) We have investigated the electrostatic, charge and orbital properties of open-ended single-wall carbon nanotubes in zigzag geometry. The calculations were performed by using the AM1-RHF semiempirical molecular orbital method. It has been found that the tubes with smaller radius behave like a metallic solid whereas the tubes with larger radius behave like a metallic hollow cylinder.
Segregation formation, thermal and electronic properties of ternary cubic CdZnTe clusters: MD simulations and DFT calculations KURBAN, MUSTAFA; Erkoç, Şakir (Elsevier BV, 2017-04-01) Surface and core formation, thermal and electronic properties of ternary cubic CdZnTe clusters are investigated by using classical molecular dynamics (MD) simulations and density functional theory (DFT.) calculations. In this work, MD simulations of the CdZnTe clusters are performed by means of LAMMPS by using bond order potential (BOP). MD simulations are carried out at different temperatures to study the segregation phenomena of Cd, Zn and Te atoms, and deviation of clusters and heat capacity. After that,...

Citation Formats

N. Dugan, “Quantum Monte Carlo methods for fermionic systems : beyond the fixed-node approximation,” Ph.D. - Doctoral Program, Middle East Technical University, 2010.