An internal coordinate quantum Monte Carlo method for calculating vibrational ground state energies and wave functions of large molecules: A quantum geometric statement function approach

1996 ◽  
Vol 105 (13) ◽  
pp. 5494-5502 ◽  
Author(s):  
Robert E. Tuzun ◽  
Donald W. Noid ◽  
Bobby G. Sumpter
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Wave Functions ◽  
Function Approach ◽  
Large Molecules ◽  
Vibrational Ground State ◽  
Quantum Monte Carlo Method ◽  
Ground State Energies

THE DIFFUSION QUANTUM MONTE CARLO METHOD: DESIGNING TRIAL WAVE FUNCTIONS FOR NiO

2003 ◽  
Vol 17 (28) ◽  
pp. 5425-5434 ◽  
Author(s):  
R. J. NEEDS ◽  
M. D. TOWLER
Keyword(s):  
Monte Carlo ◽  
Wave Function ◽  
Monte Carlo Method ◽  
Transition Metal ◽  
Quantum Monte Carlo ◽  
Monte Carlo Study ◽  
Trial Wave Function ◽  
Wave Functions ◽  
Quantum Monte Carlo Method

A brief overview of the diffusion quantum Monte Carlo method is given. The importance of the trial wave function is emphasised and we discuss how to design satisfactory forms for transition metal monoxides. Some results of a diffusion quantum Monte Carlo study of NiO are reported.

VARIATIONAL COMPUTATIONS FOR EXCITONS IN QUANTUM DOTS: A QUANTUM MONTE CARLO STUDY

2011 ◽  
Vol 25 (01) ◽  
pp. 119-130
Author(s):  
A. YILDIZ ◽  
S. ŞAKİROĞLU ◽  
Ü. DOĞAN ◽  
K. AKGÜNGÖR ◽  
H. EPİK ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Monte Carlo ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Three Dimensional ◽  
Monte Carlo Study ◽  
Wave Functions ◽  
Monte Carlo Techniques ◽  
Oscillator Basis ◽  
Ground State Energies

A study of variational wave functions for calculation of the ground-state energies of excitons confined in a two-dimensional (2D) disc-like and three-dimensional (3D) spherical parabolic GaAs quantum dots (QDs) is presented. We have used four variational trial wave functions constructed as the harmonic-oscillator basis multiplied by different correlation functions. The proposed correlation function formed by including linear expansion in terms of Hylleraas-like coordinates to the Jastrow factor is able to capture nearly exactly the ground-state energies of 3D excitons, and it properly account for the results of 2D excitons. Quantum Monte Carlo techniques combined with the proposed wave function are a powerful tool for studying excitons in parabolic QDs.

scholarly journals Comparison of Calculations for the Hubbard Model Obtained with Quantum-Monte-Carlo, Exact, and Stochastic Diagonalization

1997 ◽  
Vol 08 (02) ◽  
pp. 397-415 ◽  
Author(s):  
Thomas Husslein ◽  
Werner Fettes ◽  
Ingo Morgenstern
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Hubbard Model ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Minus Sign ◽  
Sign Problem ◽  
Quantum Monte Carlo Method ◽  
Convergence Problems ◽  
Superconducting Correlations

In this paper we compare numerical results for the ground state of the Hubbard model obtained by Quantum-Monte-Carlo simulations with results from exact and stochastic diagonalizations. We find good agreement for the ground state energy and superconducting correlations for both, the repulsive and attractive Hubbard model. Special emphasis lies on the superconducting correlations in the repulsive Hubbard model, where the small magnitude of the values obtained by Monte-Carlo simulations gives rise to the question, whether these results might be caused by fluctuations or systematic errors of the method. Although we notice that the Quantum-Monte-Carlo method has convergence problems for large interactions, coinciding with a minus sign problem, we confirm the results of the diagonalization techniques for small and moderate interaction strengths. Additionally we investigate the numerical stability and the convergence of the Quantum-Monte-Carlo method in the attractive case, to study the influence of the minus sign problem on convergence. Also here in the absence of a minus sign problem we encounter convergence problems for strong interactions.

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