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Gadolinium has long been believed to undergo a high pressure phase transitionwith a volume collapse around 5%. Theoretical explanations have focused on theidea of electrons transferring from the extended s-orbital to the compactf-orbital. However, experimental measurement has been unable to detect anyassociated change in the magnetic properties of the f-electrons. Here weresolve this discrepancy by showing that there is no significant volumecollapse, beyond what is typical in high pressure phase transformations. Wepresent density functional theory calculations of solid gadolinium under highpressure using a range of methods, and revisit the experimental situation usingX-ray diffraction (XRD). The standard lanthanide pressure-transformationsequence involving different stackings of close-packed planes: hcp to 9R todhcp to fcc to d-fcc is reproduced. The so-called "volume collapsed"high-pressure phase is shown to be an unusual stacking of close-packed planes,with Fddd symmetry and a density change less than 2%. The distorted fcc (d-fcc)structure is revealed to arise as a consequence of antiferromagnetism. Thetheoretical results are shown to be remarkably robust to various treatments ofthe f-electrons. The key result is that there is no XRD evidence for volumecollapse in Gadolinium. The sequence of phase transitions is well described bystandard DFT. There is no need for special treatment of the f-electrons orevidence of f-electron bonding. Noting previous spectroscopic evidence is thatthere is no change in the f-electrons we conclude that high pressure Gadoliniumhas no complicated f-electron physics such as Mott-Hubbard, Kondo or valencetransition.

Non-existence of the s-f transition in structures of solid gadolinium at pressure