Speaker
Description
We present a detailed density functional theory (DFT) study of the electronic structure of atomic and liquid xenon to quantify the event rates in Xe-based detectors for dark matter (DM) – electron scattering. Our main goal is to determine whether explicit modelling of the inter-atomic interactions of the liquid phase changes the predicted rates compared to state-of-the-art models based on isolated Xe atoms.
We start by identifying DFT parameters that correctly reproduce the experimental valence-electron binding energies for an isolated Xe atom. Next, we use solid crystalline xenon as a benchmark for verifying our calculations of the inter-atomic van der Waals interactions and identify a DFT setup that reproduces the experimental lattice parameter and band structure. We then model liquid xenon by creating a spatial distribution of atoms via a classical Monte-Carlo simulation with a Lennard-Jones potential, which we match with the experimental radial distribution function. We construct computationally tractable DFT input structures by sampling different regions of the distribution. We find that averaging calculations over multiple such structures gives good convergence and reproduces well the experimental refractive index of liquid xenon.
Finally, we compare the calculated form factors and rates for our DFT atom with previous semi-analytical results obtained using atomic Roothaan-Hartree-Fock wavefunctions, as well as with our DFT results for the liquid state.
| Submitted on behalf of a Collaboration? | No |
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