Random phase approximation ground state correlation energy of an interacting phonon system

1986 ◽  
Vol 323 (2) ◽  
pp. 223-226
Author(s):  
Lu Lin
Keyword(s):  
Ground State ◽  
Random Phase Approximation ◽  
Correlation Energy ◽  
Random Phase ◽  
Phase Approximation ◽  
State Correlation ◽  
Ground State Correlation

scholarly journals Ground-state correlation energy of beryllium dimer by the Bethe-Salpeter equation

2020 ◽  
Vol 8 (2) ◽  
Author(s):  
Jing Li ◽  
Ivan Duchemin ◽  
Xavier Blase ◽  
Valerio Olevano
Keyword(s):  
Ground State ◽  
Correlation Energy ◽  
Interatomic Potential ◽  
Random Phase ◽  
Difficult Problem ◽  
State Correlation ◽  
Fluctuation Dissipation ◽  
Ground State Correlation ◽  
Many Body Perturbation Theory ◽  
Beryllium Dimer

Since the ’30s the interatomic potential of the beryllium dimer Be_22 has been both an experimental and a theoretical challenge. Calculating the ground-state correlation energy of Be_22 along its dissociation path is a difficult problem for theory. We present ab initio many-body perturbation theory calculations of the Be_22 interatomic potential using the GWGW approximation and the Bethe-Salpeter equation (BSE). The ground-state correlation energy is calculated by the trace formula with checks against the adiabatic-connection fluctuation-dissipation theorem formula. We show that inclusion of GWGW corrections already improves the energy even at the level of the random-phase approximation. At the level of the BSE on top of the GWGW approximation, our calculation is in surprising agreement with the most accurate theories and with experiment. It even reproduces an experimentally observed flattening of the interatomic potential due to a delicate correlations balance from a competition between covalent and van der Waals bonding.

VARIATIONAL RANDOM PHASE APPROXIMATION FOR THE ANHARMONIC OSCILLATOR

1991 ◽  
Vol 06 (26) ◽  
pp. 2429-2435 ◽  
Author(s):  
J. DUKELSKY ◽  
P. SCHUCK
Keyword(s):  
Wave Function ◽  
Density Matrix ◽  
Ground State ◽  
Random Phase Approximation ◽  
Anharmonic Oscillator ◽  
Random Phase ◽  
Oscillator Model ◽  
Phase Approximation ◽  
Truncation Scheme

The recently derived Variational Random Phase Approximation is examined using the anharmonoic oscillator model. Special attention is paid to the ground state RPA wave function and the convergence of the proposed truncation scheme to obtain the diagonal density matrix.

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