XRD and PDF measurements were conducted at the PDF beamline (28-ID-1) at the National Synchrotron Light Source II at Brookhaven National Laboratory. X-ray measurements were performed in transmission mode with an amorphous Silicon-based flat panel detector (Perkin-Elmer) mounted orthogonal to the beam path. The sample-to-detector distance and tilt of the detector relative to the beam were refined using a Ni powder standard. The wavelength of the incident X-rays was 0.1671 Å (74.21 keV) and the sample-to-detector distances were calculated to be 219.76 mm (PDF) and 1318.98 mm (XRD). The capillaries were heated with the help of a hot-air blower at a rate of 5 C per minute. We did not use the temperature readings from the thermocouple attached to the hot-air blower because of the large temperature gradient between it and the sample. To ensure the sample was completely melted during the measurement, the data were continuously analyzed using a Constrained Matrix Factorization (CMF) method implemented at the PDF beamline. The temperature was continuously raised until a pure amorphous phase was clearly observed with CMF. All raw two-dimensional patterns were background corrected by subtracting a dark current image. Noticeable artifact regions of the detector (beam stop and damaged pixels) were masked. The corrected and masked two-dimensional detector images were then radially integrated to obtain one-dimensional powder di↵raction patterns. XRD and PDF patterns for a salt-free quartz-graphite capillary were also measured as a function of temperature, and subtracted from the individual XRD patterns. The XRD patterns corrected at the short sample-to-detector distance were corrected for PDF-specific corrections (selfabsorption, multiple scattering and Compton scattering) and converted to the structure factors S(Q), using PDFgetX3 21 over a Q-range of 0.1-22.0 Å 1 . The temperature of the molten salt was later extracted from the data using the calibrated temperature-dependent position of the Q=(002) graphite peak. To determine the temperature dependence, we measured powder patterns of the same graphite using a calibrated heating stage at a laboratory X-ray di↵ractometer. The highly-reproducible temperature dependence was fitted, and the fit was used to determine the exact temperature of the molten salt.