Obtaining statistical distributions by sampling a large number of conformations is vital for an accurate description of temperature-dependent properties of chemical systems. However, constructing distributions with 10<sup>5</sup>-10<sup>6</sup> samples is computationally challenging because of the prohibitively high computational cost of performing first-principles quantum-mechanical calculations. In this work, we present a new technique called the Effective Stochastic Potential Configuration Interaction Singles (ESP-CIS) method to obtain excitation energies. The ESP-CIS method uses random matrix theory for the construction of an effective stochastic representation of the Fock operator and combines it with linear-response theory. Here, we perform excitation calculations on PbS quantum dots (0.75-1.75 nm) at temperatures of 200-400 K. Results from a total of 15 million excitation energy calculations revealed the distributions to be sub-Gaussian in nature with negative skewness. The distributions progressively became red-shifted with increasing temperature. The study shows that random distortions in structure from the minimum-energy geometry of these quantum dots are more likely to lower the excitation energies.

Effective stochastic potential method: Investigation of temperature-dependent distributions of one million electronic excitation energies

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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