This proposal requests high-performance computing resources to perform first-principles muon-site calculations for the candidate octupolar pyrochlore Sm₂Sn₂O₇. These calculations will identify the most stable interstitial muon stopping sites and determine how the implanted muon couples to the local structural and magnetic environment. They are needed to support a future μSR experiment on the same compound, where the central goal is to search for evidence of octupolar order. In Sm₂Sn₂O₇, the μSR signal is expected to depend sensitively on the muon stopping site. If the muon occupies an interstitial site close to a Sm ion, the local magnetic field and field distribution may differ substantially from those at a more distant site. In multipolar systems such as Sm₂Sn₂O₇, the spatial dependence of the local fields can be steep, and the resulting field distribution may be broad. As a result, coherent oscillations in the μSR signal could be strongly damped or suppressed, producing an apparently exponential relaxation even if static order is present. Muon-site calculations are therefore essential for distinguishing between dynamic relaxation, absence of static order, and static order with a broad distribution of local fields. They are also important for assessing whether a μSR experiment is feasible and likely to provide useful information. The proposed calculations will use density functional theory to construct supercells of Sm₂Sn₂O₇ containing an implanted muon, relax multiple candidate muon configurations, and compare their relative energies and local structural distortions. The resulting muon–Sm distances and local coordination environments will provide the basis for estimating possible local-field distributions relevant to the μSR experiment. These tasks require systematic convergence testing of plane-wave cutoff energy, k-point sampling, and forces, as well as many independent structural relaxations starting from different initial muon positions. HPC resources are therefore required to perform the calculations reliably and within a practical timeframe. The expected outcome is a set of physically justified muon stopping sites for Sm₂Sn₂O₇, together with their local structural environments and their relevance to the observed or expected μSR relaxation. This will provide direct computational support for assessing whether μSR measurements are consistent with octupolar order and will help determine whether a strongly damped or non-oscillatory signal can still be compatible with static multipolar ordering. The main supervisors of this project are Yasmine Sassa, Martin Månsson and Anna Delin from the Applied Physics department in KTH.