Adsorbate Free Energies from DFT-Derived Translational Energy Landscapes

Waitt, Craig; Miles, Audrey R.; Schneider, William F.

doi:10.1021/acs.jpcc.1c05917

Cited by 17 publications

(14 citation statements)

References 34 publications

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“…In terms of applicability, it has to be noted that the COMD method can, like regular MD methods, only be used to integrate the free-energy difference along closed reaction paths. Therefore, the direct determination of adsorption free energies is not simple, which is also an active field of research. ,,, Additionally, quantum effects of nuclear motion, in particular zero-point vibrational energies are not included but are usually added when comparing two stationary points. Challenges that have to be overcome before the COMD method presented here can be commonly used in theoretical heterogeneous catalysis encompass the high cost of MP2 or CCSD(T) and DFT-MD calculations and the advancement of MD-type methods that efficiently allow referencing free energies to the gas phase state of guest molecules .…”

Section: Discussionmentioning

confidence: 99%

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

2022

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Herein, we propose a novel computational protocol that enables calculating free energies with improved accuracy by combining the best available techniques for enthalpy and entropy calculation. While the entropy is described by enhanced sampling molecular dynamics techniques, the energy is calculated using ab initio methods. We apply the method to assess the stability of isobutene adsorption intermediates in the zeolite H-SSZ-13, a prototypical problem that is computationally extremely challenging in terms of calculating enthalpy and entropy. We find that at typical operating conditions for zeolite catalysis (400 °C), the physisorbed π-complex, and not the tertiary carbenium ion as often reported, is the most stable intermediate. This method paves the way for sampling-based techniques to calculate the accurate free energies in a broad range of chemistry-related disciplines, thus presenting a big step forward toward predictive modeling.

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Section: Discussionmentioning

confidence: 99%

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

2022

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“…The above deduction is based on the 2D ideal gas model, which assumes that the adsorbate molecules translate freely in the xy plane. If the free translation in the plane is hindered by the barrier which is formed by the interaction of adsorbate and adsorbent, more accurate numerical results can be obtained by HT or CPES method. − …”

Section: Theorymentioning

confidence: 99%

“…It shows that 2D lattice gas model would accurately predict the adsorbate entropy when kT is less than the barrier height and that the 2D ideal gas model would accurately predict these when kT exceeds the barrier height. The barrier in HT model can also be replaced by the complete potential energy sampling (CPES). − It treats the adsorbate motion as a classical continuous system and considers the detailed energy landscape.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Entropy for a Two-Dimensional (2D) Ideal Gas with a Statistical Thermodynamic Method

et al. 2022

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Predicting adsorbate entropy is an essential prerequisite for surface science, heterogeneous catalysis, and microkinetic modeling. The linear correlation between adsorbate and gas-phase entropy has been widely found in various experiments, and it is considered as a simple and effective method to predict adsorbate entropy. In this work, the two-dimensional (2D) ideal gas model was used to calculate adsorbate entropy with the statistical thermodynamic method. The rotational entropy was obtained by solving the Schrodinger equation for a two-dimensional rotator. Combining the translational and vibrational entropy, an extended reversible adiabatic equation for 2D ideal gas can be derived, which is identical in form to the three-dimensional (3D) equation. Then the linear correlation between the 2D and 3D entropy can be proved theoretically, and the slope of this linear correlation is the heat capacity ratio. According to the characteristics of vibrational contribution to the heat capacity, the temperature is divided into three ranges, each of which has its own linear correlation. From the statistical thermodynamic computation data of benzene, perfect linear correlations can be fitted, and each slope is much close to the predicted value from our derived equation. The widely used Campbell–Sellers correlation matches our correlation in the low temperature range. We predict that there may be another linear correlation for different molecules in the medium temperature range, which is more appropriate in most heterogeneous catalytic reactions.

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“…One of the limitations of the approach is that it neglects coupling of adsorbate translations to surface atom motions. Waitt et al proposed an alternative approach, relaxing this limitation using a nudged elastic band (NEB) , minimum-energy pathway-based model to compute in-plane one-dimensional PESs …”

Section: Introductionmentioning

confidence: 99%

“…Waitt et al proposed an alternative approach, relaxing this limitation using a nudged elastic band (NEB) 9,10 minimum-energy pathwaybased model to compute in-plane one-dimensional PESs. 11 In 2021, Blondal et al proposed a sampling-based approach for evaluating the contributions of translational anharmonicity to the free energy of monatomic adsorbates. 12 The approach uses classical phase space integration and is similar to CPES, except for the fact that it includes all translational degrees of freedom of the adsorbate in the integration.…”

Section: ■ Introductionmentioning

confidence: 99%

Configuration Space Integration for Adsorbate Partition Functions: The Effect of Anharmonicity on the Thermophysical Properties of CO–Pt(111) and CH₃OH–Cu(111)

et al. 2022

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A method for computing anharmonic thermophysical properties for adsorbates on metal surfaces has been extended to include libration, or frustrated rotation. Classical phase space integration is used with Monte Carlo sampling of the configuration space to obtain the partition function of CO on Pt(111) and CH 3 OH on Cu(111). A minima-preserving neural network potential energy surrogate is used within the integration routines. Direct state counting using discrete variable representation is used to benchmark the results. We find that the phase space integration approach is in excellent agreement with the direct state counting results. Comparison with standard models such as the harmonic oscillator indicates that anharmonicity contributes significantly to the thermodynamic properties of CH 3 OH on Cu(111). We find that there is also a considerable difference between the harmonic oscillator and phase space integration for CO on Pt(111), although the discrepancy can largely be attributed to the presence of multiple binding sites within the unit cell. We demonstrate that a multisite harmonic oscillator model might be sufficient for . A more thorough description of the potential energy surface, which can be achieved with phase space integration, is necessary for weakly bound adsorbates such as CH 3 OH. The thermophysical properties were used to calculate free energies of adsorption on the respective metals, and subsequently the equilibrium constants and Langmuir isotherms in relevant temperature ranges. The results show that the choice of model to obtain partition functions greatly affects the resulting surface coverages in kinetic models.

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Adsorbate Free Energies from DFT-Derived Translational Energy Landscapes

Cited by 17 publications

References 34 publications

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

Calculation of Entropy for a Two-Dimensional (2D) Ideal Gas with a Statistical Thermodynamic Method

Configuration Space Integration for Adsorbate Partition Functions: The Effect of Anharmonicity on the Thermophysical Properties of CO–Pt(111) and CH₃OH–Cu(111)

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Adsorbate Free Energies from DFT-Derived Translational Energy Landscapes

Cited by 17 publications

References 34 publications

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

Toward Computing Accurate Free Energies in Heterogeneous Catalysis: a Case Study for Adsorbed Isobutene in H-ZSM-5

Calculation of Entropy for a Two-Dimensional (2D) Ideal Gas with a Statistical Thermodynamic Method

Configuration Space Integration for Adsorbate Partition Functions: The Effect of Anharmonicity on the Thermophysical Properties of CO–Pt(111) and CH3OH–Cu(111)

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Configuration Space Integration for Adsorbate Partition Functions: The Effect of Anharmonicity on the Thermophysical Properties of CO–Pt(111) and CH₃OH–Cu(111)