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Spatial Separation of Molecular Conformers and Clusters

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A fast variational Gaussian wavepacket method: size-induced structural transitions in large neon clusters.

Ionuţ Georgescu¹, Vladimir A Mandelshtam

¹Chemistry Department, University of California, Irvine, California 92697, USA. ionut.georgescu@uci.edu

The Journal of Chemical Physics

|October 28, 2011

Summary

We developed a fast variational Gaussian wavepacket (VGW) method to efficiently compute thermodynamic properties of many-body systems. This accelerated approach reduces computational scaling and accurately models quantum Lennard-Jones clusters.

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Area of Science:

Computational physics
Quantum mechanics
Statistical mechanics

Background:

The variational Gaussian wavepacket (VGW) approximation offers an alternative to path integral Monte Carlo for calculating thermodynamic properties of many-body systems.
VGW provides direct access to the thermal density matrix and is efficient for Monte Carlo methods, operating in a 3N-dimensional configuration space for N-body systems.

Purpose of the Study:

To accelerate the VGW method by optimizing the Gaussian width matrix.
To reduce the computational scaling of the VGW method from O(N^3) to O(N^2).
To apply the accelerated method to study structural motifs in quantum Lennard-Jones clusters.

Main Methods:

Implemented a fast-VGW (fast-variational Gaussian wavepacket) method by retaining only short-range correlations in the Gaussian width matrix.
Reduced the computational complexity from O(N^3) to O(N^2) while maintaining accuracy.
Applied the fast-VGW method to analyze Ne(N) clusters up to N = 6500 atoms.

Main Results:

Achieved a significant reduction in computational scaling for the VGW method.
Successfully applied the fast-VGW method to large quantum Lennard-Jones clusters.
Investigated the competition between icosahedral and decahedral structures in Ne(N) clusters.

Conclusions:

The fast-VGW method provides a computationally efficient approach for studying thermodynamic properties of quantum systems.
The method enables accurate modeling of large atomic clusters.
The study sheds light on the structural preferences of Ne(N) clusters.