Korol Group

Research Focus Areas

Quantum Dynamics

Path integral methods, ring polymer molecular dynamics, semiclassical approaches

Chemical Kinetics

Reaction rate theory, isotope effects, environmental effects on chemical reactions

Open Quantum Systems

Quantum transport, electron-phonon interactions, spectral density modeling

1. Robust Purely Optical Signatures of Floquet States in Laser-Dressed Crystals

   V Tiwari, R Korol and I Franco*,    Phys. Rev. Lett.   2025    135 (18) , 186901,   10.1103/5ywx-7dbs.

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   We outline a simple way to detect elusive light-induced states in optically driven materials by analyzing how they absorb light. These so-called Floquet states, which form when materials interact with strong laser fields, are key to controlling material properties on demand—but until now, they've been extremely difficult to observe. We show that Floquet states leave clear, detectable signatures in the optical absorption spectrum, including new absorption peaks in regions where the material is normally transparent.

2. High-Frequency Tails in Spectral Densities

   R Korol*, X Chen and I Franco*,    J. Phys. Chem. A   2025    129 (15) , 3587-3596,   10.1021/acs.jpca.5c00943.

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   We show that the computations of relaxation rate in solution are highly sensitive to the choice of representation of the environmental spectral density (SD). The key reason is that electronic relaxation is dominated by the resonant contribution from the high-frequency tails of the SD, which can vary significantly between strategies. We provide a simple transformation that recovers the correct relaxation rates in quantum simulations constrained by algorithmic or physical limitations on the shape of the SD.

3. Stable isotope equilibria in the dihydrogen-water-methane-ethane-propane system. Part 2: Experimental determination of hydrogen isotopic equilibrium for ethane-H₂ from 30 to 200 °C and propane-H₂ from 75 to 200 °C

   A C Turner*, R Korol, M Bill and D A Stolper,    Geochim. Cosmochim. Acta   2025    396 , 91-106,   10.1016/j.gca.2025.02.033.

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   We compare experimental hydrogen isotopic equilibrium with high-level theoretical calculations and provide a preferred polynomial fit. Comparison of these fractionation factors with a compilation of ~500 compiled environmental gas samples supports the proposal that many (~50%) of these natural gas samples exhibit hydrogen isotopic compositions consistent with having formed in or attained methane-ethane-propane hydrogen isotopic equilibrium over geologically relevant temperatures for formation and storage (50-300°C).

4. Stable isotope equilibria in the dihydrogen-water-methane-ethane-propane system. Part 1: Path-integral calculations with CCSD(T) quality potentials

   R Korol*, A C Turner, A Nandi, J M Bowman, W A Goddard and D A Stolper,    Geochim. Cosmochim. Acta   2025    396 , 71-90,   10.1016/j.gca.2025.02.028.

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   We analyze the relative importance of various approximations that are commonly employed when isotopic equilibria are evaluated. We find that clumped isotope effects can be calculated using computational methods. In contrast, fractionation and site preferences benefit from the use of the higher level CCSD(T) potentials, accounting for anharmonic effects, and corrections to Born-Oppenheimer approximation.

5. Experimental and theoretical determinations of hydrogen isotopic equilibrium in the system CH₄-H₂-H₂O from 3 to 200 °C

   A C Turner, R Korol, D L Eldridge, M Bill, M E Conrad, T F Miller and D A Stolper*,    Geochim. Cosmochim. Acta   2021    314 , 223-269,   10.1016/j.gca.2021.04.026.

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   We provide calibrations of the equilibrium H/D and ¹³C/¹²C fractionation based on experiments and PIMC calculations. We find that isotopic compositions of some microbial gases from marine sedimentary, coalbed, and shale environments are consistent with the H and C equilibria.

6. Dimension-free path-integral molecular dynamics without preconditioning

   R Korol, J L Rosa-Raíces, N Bou-Rabee and T F Miller*,    J. Chem. Phys.   2020    152 (10) , 104102,   10.1063/1.5134810.

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   We further improve upon the standard algorithm for T-RPMD via a novel implementation of the Cayley modification [R Korol et al., J. Chem. Phys. 151, 124103 (2019)]. This allows for a substantial increase in timestep size - three-fold for the simulations of liquid water - at no extra cost.

7. Comparison of Experimental vs Theoretical Abundances of ¹³CH₃D and ¹²CH₂D₂ for Isotopically Equilibrated Systems from 1 to 500 °C

   D L Eldridge, R Korol, M K Lloyd, A C Turner, M A Webb, T F Miller and D A Stolper*,    ACS Earth Space Chem.   2019    3 (12) , 2747-2764,   10.1021/acsearthspacechem.9b00244.

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   We study equilibrium clumping of heavy isotopes in methane. Using heavy isotope clumping, one can determine the temperature of methane when it was formed. We have extended the range of temperatures to cover all biologically and geologically relevant temperatures. Experimental clumping-temperature calibration is confirmed by state-of-the-art theoretical method - PIMC.

8. Cayley modification for strongly stable path-integral and ring-polymer molecular dynamics

   R Korol, N Bou-Rabee and T F Miller*,    J. Chem. Phys.   2019    151 (12) , 124103,   10.1063/1.5120282.

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   We present a novel implementation of the Cayley modification that ensures exact trajectories with respect to a modified Hamiltonian when the free ring-polymer limit is employed. This leads to strongly stable dynamics that enables considerably larger timesteps relative to existing approaches with other thermostatting methods or bare velocity Verlet integrators.

9. Machine Learning Prediction of DNA Charge Transport

   R Korol and D Segal*,    J. Phys. Chem. B   2019    123 (13) , 2801-2811,   10.1021/acs.jpcb.8b12557.

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   We present a machine learning model that enables low-cost prediction of the electrical conductance of millions of long double-stranded DNA (dsDNA) sequences, reducing computational costs by several orders of magnitude. The algorithm is trained on short DNA nanojunctions with n = 3-7 base pairs.

10. From Exhaustive Simulations to Key Principles in DNA Nanoelectronics

    R Korol and D Segal*,    J. Phys. Chem. C   2018    122 (8) , 4206-4216,   10.1021/acs.jpcc.7b12744.

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    Conductance of DNA molecules is not well-understood in the light of opposing experimental results. The situation is also complicated, because there are exponentially many different sequences, and many of them conduct current in a drastically different way. Here we study the conductance of DNA molecules computationally and identify several general principles that could guide the experiments.

11. ProbeZT: Simulation of transport coefficients of molecular electronic junctions under environmental effects using Büttiker's probes

    R Korol, M Kilgour and D Segal*,    Comput. Phys. Commun.   2018    224 , 396-404,   10.1016/j.cpc.2017.10.005.

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    Our in-house quantum transport package, ProbeZT, calculates how readily electricity and heat moves across a given system. One can use it to identify molecules that are: good conductors, perfect insulators, excellent thermoelectrics and many more. In particular, we show the package applied to a linear conducting chain (like a polymer) and to a double-stranded DNA molecule.

12. Thermopower of molecular junctions: Tunneling to hopping crossover in DNA

    R Korol, M Kilgour and D Segal*,    J. Chem. Phys.   2016    145 (22) , 224702,   10.1063/1.4971167.

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    We examine the DNA molecules, that show a change in behavior in conductance and thermopower beyond a certain length, studied experimentally in Li et al. [Nat. Commun. 7, 11294 (2016)]. We show that the change in thermoelectric trends is caused by a change of the mechanism, by which a molecule conducts current from quantum mechanical tunneling to classical hopping.

13. Reactions of Boron-Derived Radicals with Nucleophiles

    L E Longobardi, P Zatsepin, R Korol, L Liu, S Grimme and D W Stephan*,    J. Am. Chem. Soc.   2016    139 (1) , 426-435,   10.1021/jacs.6b11190.

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    We utilize a series of borocyclic radicals, that are both bulky and with their SOMO density delocalized. Their electrophilic reactivity together with their considerable steric hinderance allows us to make several nice zwitterionic compounds with phosphines and other nucleophiles utilizing Frustrated Lewis Pair chemistry.

14. Size Stabilizers in Two-electrode Synthesis of ZnO Nanorods

    R V Korol*, O M Yanchuk, O V Marchuk, V F Orlov, I A Moroz and O A Vyshnevskyi,    Phys. Chem. Solid St.   2021    22 (2) , 380-387,   10.15330/pcss.22.2.380-387.

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    We modify and optimize a synthesis of ZnO nanoparticles by electrodeposition by adding auxiliary stabilizers to reduce the size and narrow its distribution in the target product.