# A Benchmark Quantum Monte Carlo Study of Molecular Crystal Polymorphism: A Challenging Case for Density-Functional Theory

 Title: A Benchmark Quantum Monte Carlo Study of Molecular Crystal Polymorphism: A Challenging Case for Density-Functional Theory Author: Hongo, Kenta; Watson, Mark A.; Iitaka, Toshiaki; Aspuru-Guzik, Alan Note: Order does not necessarily reflect citation order of authors. Citation: Watson, Mark A., Kenta Hongo, Toshiaki Iitaka, and Alan Aspuru-Guzik. 2012. A Benchmark Quantum Monte Carlo Study of Molecular Crystal Polymorphism: A Challenging Case for Density-Functional Theory. In Advances in Quantum Monte Carlo, ed. Shigenori Tanaka, Stuart M. Rothstein, and William A. Lester, 1094:101-117. Washington, DC: American Chemical Society. Access Status: Full text of the requested work is not available in DASH at this time (“dark deposit”). For more information on dark deposits, see our FAQ. Full Text & Related Files: aspuru-guzik-benchmark QMC.pdf (487.3Kb; PDF) Abstract: We have applied the diffusion Monte Carlo (DMC) method, for the first time, to an organic molecular crystal (para-diiodobenzene) in order to determine the relative stability of its two well- known polymorphs. The DMC result predicts that the $$\alpha$$ phase is more stable than the $$\beta$$ phase at zero temperature, in agreement with experiment. In comparison, we evaluated four commonly-used local, semi-local and hybrid density functionals. We conclude that while density-functional theory (DFT) may provide the most practical method for including the effects of electron correlation, conventional functionals cannot be considered reliable for determining highly accurate energies in such systems. Published Version: doi:10.1021/bk-2012-1094.ch009 Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10057424 Downloads of this work: