Development of a Multicenter Density Functional Tight Binding Model for Plutonium Surface Hydriding

Abstract

We detail the creation of a multicenter density functional tight binding (DFTB) model for hydrogen on δ-plutonium, using a framework of new Slater-Koster interaction parameters and a repulsive energy based on the Chebyshev Interaction Model for Efficient Simulation (ChIMES), where two- and three-center atomic interactions are represented by linear combinations of Chebyshev polynomials. We find that our DFTB/ChIMES model yields a total electron density of states for bulk δ-Pu that compares well to that from Density Functional Theory, as well as to a grid of energy calculations representing approximate H dissociation paths on the δ-Pu (100) surface. We then perform molecular dynamics simulations and minimum energy pathway calculations to determine the energetics of surface dissociation and subsurface diffusion on the (100) and (111) surfaces. Our approach allows for the efficient creation of multicenter repulsive energies with a relatively small investment in initial DFT calculations. Our efforts are particularly pertinent to studies that rely on quantum calculations for interpretation and validation, such as experimental determination of chemical reactivity both on surfaces and in condensed phases.

Synthesis of functionalized nitrogen-containing polycyclic aromatic hydrocarbons and other prebiotic compounds in impacting glycine solutions

“…44,48,[53][54][55][56] It was previously shown that DFTB can recover DFT-level accuracy for systems under reactive conditions through tuning E Rep to DFT computed forces or training sets. [46][47][48]50,[57][58][59][60][61] Hence, most of the generic E Rep interactions in the mio-1-1 parameterization were replaced with force-matched ones (discussed below) that were determined specically for aqueous glycine chemistry. Universal force eld dispersion terms 62 were used for E Disp .…”

“…[37][38][39] However, DFT-MD simulations are too computationally intensive to probe beyond picosecond and nanometer time and length scales, whereas chemical equilibrium under these conditions can take nanoseconds or longer to be achieved. [40][41][42] Semi-empirical methods such as the density functional tight binding (DFTB) method [43][44][45][46][47][48] combine approximate quantum mechanics with empirical functions to offer an efficient alternative that is orders of magnitude less computationally intensive while retaining a high degree of accuracy. The computational efficiency of DFTB allows for initiating many independent simulations concurrently to generate trajectories that can approach chemical equilibrium timescales.…”

Density-functional tight-binding: basic concepts and applications to molecules and clusters

“…Optical properties of natural pigments (flavonols) adsorbed on boron nitride nanotubes were also analyzed using DFTB (Figure 8) [315]. Some DFTB surface adsorption studies have also given rise to reactivity studies, for example water splitting on anatase (001) [316] or H 2 dissociation on plutonium [317].…”

First-Principles Study of Nitrogen Adsorption and Dissociation on PuH2 (111) Surface

“…Their influential investigations of molecular hydrogen interaction with δ-Pu are of great significance, as they compared the dissociation barriers with different surfaces and found the most favorable dissociation channel [18,19]. Goldman's innovative calculation provided valuable insight into the H 2 dissociation pathways with an energy map, and also indicated that the dissociation reaction is highly active even at ambient conditions [20,21]. In a thorough study of H 2 interaction with PuO 2 , Yu and Meng compared various adsorption sites to evaluate H 2 dissociation and atomic H diffusion energy barriers.…”