Molecular tailoring approach in conjunction with MP2 and Ri‐MP2 codes: A comparison with fragment molecular orbital method

Abstract

Many Divide-and-Conquer based approaches are being developed to overcome the high scaling problem of the ab initio methods. In this work, one such method, Molecular Tailoring Approach (MTA) has been interfaced with recently developed efficient Møller-Plesset second order perturbation theory (MP2) codes viz. IMS-MP2 and RI-MP2 to reap the advantage of both. An external driver script is developed for implementing MTA at the front-end and the MP2 codes at the back-end. The present version of the driver script is written only for a single point energy evaluation of a molecular system at a fixed geometry. The performance of these newly developed MTA-IMS-MP2 and MTA-RI-MP2 codes is extensively benchmarked for a variety of molecular systems vis-à-vis the corresponding actual runs. In addition to this, the performance of these programs is also critically compared with Fragment Molecular Orbital (FMO), another popular fragment-based method. It is observed that FMO2/2 is superior to FMO3/2 and MTA with respect to time advantage; however, the errors of FMO2 are much beyond chemical accuracy. However, FMO3/2 is a highly accurate method for biological systems but is unsuccessful in case of water clusters. MTA produces estimates with errors within 1 kcal/mol uniformly for all systems with reasonable time advantage. Analysis carried out employing various basis sets shows that FMO gives its optimum performance only for basis sets, which does not include diffuse functions. On the contrary, MTA performance is found to be similar for any basis set used.

Accurate vibrational spectra via molecular tailoring approach: A case study of water clusters at MP2 level

“…It has been observed in the earlier works that for a given set of fragments, the error in MTA energy is not sensitive to the basis set used and hence can be corrected through the grafting procedure. 49,50,56 The method of correcting the energy involves the grafting of the error at a smaller basis (sb) set onto the final desired larger basis (lb) set. 49,50 The error in MTA (and presumably also for all other fragment-based methods) seems to originate mainly from HF rather than the MP2 level treatment.…”

“…The current methodology is amenable to parallelization, in line with the earlier efforts in our group. 27,56,71 Furthermore, the present methodology can be extended to any level of theory. In summary, in terms of both accuracy and feasibility, the MTA coupled with the grafting procedure is expected to serve as an effective tool for high-level quantum chemical investigations of large molecular systems.…”

“…The grafting correction hinges upon the fact that the errors in MTA vis-à-vis their full calculation counterparts show only a small dependence on the basis sets. 49,50,56 These grafted values of the Hessian and dipole derivatives are further utilized for the estimation of accurate vibrational spectra of molecular systems via the normal mode analyses. This method for estimating the vibrational spectra has been tested out on both neutral [(H 2 O) 16 12 ] employing either MP2/aug-cc-pVDZ or MP2/6-311+G * * level of theory.…”

Application of second-order Møller–Plesset perturbation theory with resolution-of-identity approximation to periodic systems

“…[33][34][35] Recently, we have developed an efficient parallel RI-MP2 energy algorithm and tested it with molecules consisting of up to 300 atoms and 4000 AOs. 36,37 Applications of the RI approximation to local MP2 ͑Refs. 38-41͒ and AO Laplace-transformed MP2 ͑Ref.…”

Theory and Calculations of Molecules Containing Heavier Main Group Elements and Fullerenes Encaging Transition Metals: Interplay with Experiment

“…148 The developed MP2 code was applied to the fragment molecular orbital (FMO) method 149 and molecular tailoring approach (MTA). 150 In addition, the two-level hierarchical parallelization of MP2 calculations was performed for the divide-and-conquer (DC) method. 151 Even with the efficient program, the computational cost and the sizes of memory and disk required for MP2 calcula- tions increase drastically as molecular sizes increase.…”