Roman Fanta

All Publications

• Molecular reference corrections for quantum Monte Carlo adsorption energies PHYSICAL REVIEW B Fanta, R., Bajdich, M. 2026; 114 (12)

  View details for DOI 10.1103/cgmx-p5n9

  View details for Web of Science ID 001850014800001

• Why Nondynamic Correlation Matters forpipiStacking? Lessons from the Benzene Dimer. The journal of physical chemistry letters Fanta, R., Jurecka, P., Dubecky, M. 2025: 10982-10988

  Abstract

  Two leading methods for benchmarking pipi interactions are fixed-node diffusion Monte Carlo (DMC) and coupled cluster with singles, doubles, and perturbative triples [CCSD(T)]. The parallel-displaced benzene dimer (BZPD) is a key model for assessing the performance of theoretical approaches in describing these interactions. Reference calculations, symmetry-adapted perturbation theory, and correlation energy decompositions highlight the subtle but critical role of weak nondynamic correlation effects in achieving benchmark interaction energies for BZPD. While single-determinant DMC (SDDMC), using nodes from DFT or Hartree-Fock, performs well for many noncovalent systems, our analysis shows that neglecting weak nondynamic correlations in mean-field trial wave functions leads to systematic underbinding in SDDMC energy differences, in contrast to CCSD(T)/CBS results. These findings underscore the limitations of SDDMC for describing pipi interactions and emphasize the need for improved nodal descriptions to establish DMC as a reliable benchmark method for larger complexes.

  View details for DOI 10.1021/acs.jpclett.5c02576

  View details for PubMedID 41084851

• Spin State Modulation in M-N-C Single-Atom Catalysts for Oxygen Electrocatalysis ACS CATALYSIS Jung, H., Fanta, R., Hossain, M., Bajdich, M. 2025

  View details for DOI 10.1021/acscatal.5c04591

  View details for Web of Science ID 001570163000001

• Resolution of Selectivity Steps of CO Reduction Reaction on Copper by Quantum Monte Carlo. The journal of physical chemistry letters Fanta, R., Bajdich, M. 2025: 1494-1500

  Abstract

  Electrochemical reduction of carbon monoxide to valuable fuels and chemicals on copper surfaces remains a challenging area in catalysis due to a limited understanding of adsorption mechanisms and reaction pathways. Although density functional theory (DFT)-based studies have investigated these processes, their accuracy varies across different functionals. Here, we present the application of fixed-node diffusion Monte Carlo (FNDMC) to benchmark the adsorption energies of CO*, H*, and key CO reduction reaction (CORR) intermediates, COH* and CHO* on the Cu(111) surface. Our results for CO* and H* adsorption energies closely align with experimentally measured chemisorption reactions, highlighting the limitations of DFT and providing site-specific energy comparisons that are often not available experimentally. Additionally, we explore the effect of explicit solvation, demonstrating how water stabilizes the COH* over CHO*, thus suggesting a critical role of COH* in CORR. Finally, we release our high-accuracy FNDMC benchmarks for testing and developing new DFT functionals for electrocatalysis. Overall, this study underscores the potential of FNDMC for detailed surface chemistry studies and offers new insights into catalytic processes.

  View details for DOI 10.1021/acs.jpclett.4c03409

  View details for PubMedID 39898589

• Toward automated screening of band gap sensitivity in 2D materials JOURNAL OF PHYSICS-MATERIALS Fanta, R., Dubecky, M. 2023; 6 (4)

  View details for DOI 10.1088/2515-7639/acef97

  View details for Web of Science ID 001053267300001

• Noncovalent Interactions by the Quantum Monte Carlo Method: Strong Influence of Isotropic Jastrow Cutoff Radii JOURNAL OF CHEMICAL THEORY AND COMPUTATION Fanta, R., Dubecky, M. 2021; 17 (7): 4242-4249

  Abstract

  We present a paradigmatic example of a strong effect of Jastrow cutoff radii setup on the accuracy of noncovalent interaction energy differences within one-determinant Slater-Jastrow fixed-node diffusion Monte Carlo (1FNDMC) simulations using isotropic Jastrow terms and effective-core potentials. Analysis of total energies, absolute and relative errors, and local energy variance of energy differences vs the reference results suggests a simple procedure to marginalize the related biases. The presented data showcase improvements in dispersion-bounded systems within such a 1FNDMC method.

  View details for DOI 10.1021/acs.jctc.1c00467

  View details for Web of Science ID 000674289800033

  View details for PubMedID 34169721

• Benchmarking lattice energy of a model 1D molecular HF crystal THEORETICAL CHEMISTRY ACCOUNTS Fanta, R., Kolesar, V., Simunek, J., Dubecky, M. 2020; 139 (5)

  View details for DOI 10.1007/s00214-020-02601-3

  View details for Web of Science ID 000529680000001

• Toward Accurate Hydrogen Bonds by Scalable Quantum Monte Carlo JOURNAL OF CHEMICAL THEORY AND COMPUTATION Dubecky, M., Jurecka, P., Mitas, L., Ditte, M., Fanta, R. 2019; 15 (6): 3552-3557

  Abstract

  Single-determinant (SD) fixed-node diffusion Monte Carlo (FNDMC) gains popularity as a benchmark method scalable to large noncovalent systems, although its accuracy limits are not yet fully mapped out. We report on an interesting example of significant SD FNDMC accuracy variations in middle-sized hydrogen-bonded dimer complexes, formic acid (FA) vs methanediol (MD), distinct by the maximum bond order (2 vs 1). While the traditional SD FNDMC schemes based on bias cancellation are capable of achieving benchmark (2%) accuracy for MD, this has not been the case for FA. We identify the leading systematic error source in energy differences and show that suitably designed Jastrow factors enable SD FNDMC to reach the reference accuracy for FA. This work clearly illustrates the varying accuracy of the present-day SD FNDMC at the 0.1 kcal/mol scale for a particular set of systems but also points out promising routes toward alleviation of these shortcomings, still within the single-reference framework.

  View details for DOI 10.1021/acs.jctc.9b00096

  View details for Web of Science ID 000471728500011

  View details for PubMedID 31026158