We provide insights into the atomistic details of the ultrafast spatially resolved breakdown of the insulating ${\mathrm{M}}_1$ phase in bulk ${\mathrm{VO}}_2$ employing an ab initio technique based on dynamical mean-field theory and time-dependent density-functional theory. We find that the system is initially metallized preferentially along the vanadium-dimer chains, with a subsequent growth of metallic bubbles elongated along the ${\mathrm{C}}_{\mathrm{R}}$ direction. We trace the breakdown of the insulating phase to the two types of oxygen atoms resulting from vanadium dimerization, which produces a nontrivial charge-density modulation in the oxygen-atom chains with significant charge transfer to the interdimer bond. These results, which are in qualitative agreement with experimental data, shed light on the important role of the nonequivalent oxygen atoms in the spatially resolved ultrafast response of this strongly correlated insulator.

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• Metal-insulator transition
• Photoinduced effect
• Mott insulators
• Strongly correlated systems
• First-principles calculations