Toward an Accurate and Inexpensive Estimation of CCSD(T)/CBS Binding Energies of Large Water Clusters

Abstract

Owing to the steep scaling behavior, highly accurate CCSD(T) calculations, the contemporary gold standard of quantum chemistry, are prohibitively difficult for moderate- and large-sized water clusters even with the high-end hardware. The molecular tailoring approach (MTA), a fragmentation-based technique is found to be useful for enabling such high-level ab initio calculations. The present work reports the CCSD(T) level binding energies of many low-lying isomers of large (H2O)n (n = 16, 17, and 25) clusters employing aug-cc-pVDZ and aug-cc-pVTZ basis sets within the MTA framework. Accurate estimation of the CCSD(T) level binding energies [within 0.3 kcal/mol of the respective full calculation (FC) results] is achieved after effecting the grafting procedure, a protocol for minimizing the errors in the MTA-derived energies arising due to the approximate nature of MTA. The CCSD(T) level grafting procedure presented here hinges upon the well-known fact that the MP2 method, which scales as O(N(5)), can be a suitable starting point for approximating to the highly accurate CCSD(T) [that scale as O(N(7))] energies. On account of the requirement of only an MP2-level FC on the entire cluster, the current methodology ultimately leads to a cost-effective solution for the CCSD(T) level accurate binding energies of large-sized water clusters even at the complete basis set limit utilizing off-the-shelf hardware.

Large‐Sized Ammonia Clusters and Solvation Energies of the Proton in Ammonia

“…Elsewhere, we found that the structures of large‐sized neutral ammonia clusters exhibit the same behavior as those of large‐sized neutral water clusters . Sahu et al reported that the most stable isomers of the water 25‐mer are cage‐like structures with central solvated water molecule.…”

“…Elsewhere, we found that the structures of large-sized neutral ammonia clusters exhibit the same behavior as those of largesized neutral water clusters. [59][60][61][62] Sahu et al [59] reported that the most stable isomers of the water 25-mer are cage-like structures with central solvated water molecule. Recently, Rakshit et al [61] investigated the structures of neutral water clusters for n = 32 and n = 33 using Monte Carlo simulations and further energies calculations using DFT and ab initio methods.…”

Molecular Tailoring Approach for the Estimation of Intramolecular Hydrogen Bond Energy

“…The molecular tailoring approach (MTA) is a fragmentation-based technique developed by Gadre et al [ 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. Within MTA, a spatially extended molecular system under consideration is partitioned into a set of overlapping fragments (called the “main fragments”) on which ab initio calculations for one-electron property or the energy are carried out.…”

“…Thus, it was felt necessary to come up with a direct theoretical method for a reliable estimation of IHB energy. Deshmukh and Gadre [ 66 , 67 ] proposed such a procedure, based on the in-house developed molecular tailoring approach (MTA) for the ab initio treatment of large molecular systems [ 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. The MTA currently enables the calculation of one-electron properties, geometry optimization, and the calculation of vibrational infrared and Raman spectra of large molecules/clusters using DFT or correlated methods.…”

Binding energies and isomer distribution of neutral acetonitrile clusters

“…Moreover, the structures of the nitrous oxide clusters are also stabilized by dipole–dipole interactions. However, we found that acetonitrile clusters exhibits completely different structural arrangements as compared to neutral water clusters 20‐22,29,61‐64 and neutral ammonia clusters 35,65‐67 …”