scholarly journals Analysis of the basis set superposition error in molecular dynamics of hydrogen-bonded liquids: Application to methanol

2012 ◽  
Vol 137 (10) ◽  
pp. 104506 ◽  
Author(s):  
Marc Van Houteghem ◽  
Toon Verstraelen ◽  
An Ghysels ◽  
Louis Vanduyfhuys ◽  
Michel Waroquier ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Basis Set ◽  
Basis Set Superposition Error ◽  
Hydrogen Bonded

Counterpoise-Corrected Potential Energy Surfaces of Simple Hydrogen-Bonded Systems

1998 ◽  
Vol 63 (9) ◽  
pp. 1343-1354 ◽  
Author(s):  
Pavel Hobza ◽  
Zdeněk Havlas
Keyword(s):  
Potential Energy Surfaces ◽  
Correlation Energy ◽  
Linear Structure ◽  
Water Dimer ◽  
Basis Set ◽  
Basis Sets ◽  
Basis Set Superposition Error ◽  
Gradient Optimization ◽  
Intermolecular Distances ◽  
Hydrogen Bonded

Geometric and energetic characteristics of various simple hydrogen-bonded complexes (water dimer, hydrogen fluoride dimer, formamide dimer, formic acid dimer, glycine dimer) have been studied by gradient optimization, which a priori eliminates the basis set superposition error (BSSE) by using the counterpoise (CP) method, as well as by the standard gradient optimization. Calculations were done at the Hartree-Fock, correlated MP2 and DFT levels with small- and medium-basis sets. The CP-corrected and standard PESs differ, depending on the theoretical level used. Larger differences were found if the correlation energy was included. Intermolecular distances from the CP-corrected PES are consistently longer, and the respective difference may be significant (≈0.1 A). The stabilization energies obtained from the CP-corrected PES are always larger than those from the standard PES. Optimization at the standard PES might result in a wrong structure. For example, the "quasi-linear" structure of the (HF)2 (global minimum) does not exist at the standard MP2/6-31G** and DFT/B3LYP/6-31G** PESs and it is found only when passing to the respective CP-corrected PESs.

scholarly journals An Investigation into the Approximations Used in Wave Packet Molecular Dynamics for the Study of Warm Dense Matter

Plasma ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 294-308
Author(s):  
William A. Angermeier ◽  
Thomas G. White
Keyword(s):  
Molecular Dynamics ◽  
Wave Packet ◽  
Hydrogen Plasma ◽  
Valence Bond ◽  
Dense Matter ◽  
Basis Set ◽  
Warm Dense Matter ◽  
Scaling Parameters ◽  
Oppenheimer Approximation ◽  
Semi Empirical

Wave packet molecular dynamics (WPMD) has recently received a lot of attention as a computationally fast tool with which to study dynamical processes in warm dense matter beyond the Born–Oppenheimer approximation. These techniques, typically, employ many approximations to achieve computational efficiency while implementing semi-empirical scaling parameters to retain accuracy. We investigated three of the main approximations ubiquitous to WPMD: a restricted basis set, approximations to exchange, and the lack of correlation. We examined each of these approximations in regard to atomic and molecular hydrogen in addition to a dense hydrogen plasma. We found that the biggest improvement to WPMD comes from combining a two-Gaussian basis with a semi-empirical correction based on the valence-bond wave function. A single parameter scales this correction to match experimental pressures of dense hydrogen. Ultimately, we found that semi-empirical scaling parameters are necessary to correct for the main approximations in WPMD. However, reducing the scaling parameters for more ab-initio terms gives more accurate results and displays the underlying physics more readily.

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