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

• Published in: The Journal of chemical physics 2011-10, Vol.135 (15), p.154106-154106-6
• Main Authors: Georgescu, Ionuţ, Mandelshtam, Vladimir A.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.3651473

The variational Gaussian wavepacket (VGW) approximation provides an alternative to path integral Monte Carlo for the computation of thermodynamic properties of many-body systems at thermal equilibrium. It provides a direct access to the thermal density matrix and is particularly efficient for Monte Carlo approaches, as for an N -body system it operates in a non-inflated 3 N -dimensional configuration space. Here, we greatly accelerate the VGW method by retaining only the relevant short-range correlations in the (otherwise full) 3 N × 3 N Gaussian width matrix without sacrificing the accuracy of the fully coupled VGW method. This results in the reduction of the original $\mathcal {O}(N^3)$ O ( N 3 ) scaling to $\mathcal {O}(N^2)$ O ( N 2 ) . The fast-VGW method is then applied to quantum Lennard-Jones clusters with sizes up to N = 6500 atoms. Following Doye and Calvo [ JCP 116 , 8307 ( 2002 ) 10.1063/1.1469616 ] we study the competition between the icosahedral and decahedral structural motifs in Ne N clusters as a function of N .