The interaction between two chemically identical charge-regulated surfaces is studied using the classical density functional theory. In contrast to common expectations and assumptions, under certain realistic conditions we find a spontaneous emergence of disparate charge densities on the two surfaces. The surface charge densities can differ not only in their magnitude, but quite unexpectedly, even in their sign, implying that the electrostatic interaction between the two chemically identical surfaces can be attractive instead of repulsive. Moreover, an initial symmetry with equal charge densities on both surfaces can also be broken spontaneously upon decreasing the separation between the two surfaces. The origin of this phenomenon is a competition between the adsorption of ions from the solution to the surface and the interaction between the adsorbed ions already on the surface. These findings are fundamental for the understanding of the forces between colloidal objects and, in particular, they are bound to strongly influence the present picture of protein interaction.

中文翻译：

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电荷调节表面的自发对称破坏†

使用经典的密度泛函理论研究了两个化学上相同的电荷调节表面之间的相互作用。与通常的期望和假设相反，在某些现实条件下，我们发现两个表面上电荷密度的自发出现。表面电荷密度不仅在大小上可能不同，而且甚至在符号上也出乎意料地不同，这意味着两个化学上相同的表面之间的静电相互作用可以吸引而不是排斥。此外，当减小两个表面之间的间隔时，两个表面上具有相等电荷密度的初始对称性也可以自发地破坏。这种现象的起因是离子从溶液到表面的吸附与已经在表面上的吸附离子之间的相互作用之间的竞争。这些发现对于理解胶体之间的作用力至关重要，尤其是它们必将极大地影响蛋白质相互作用的现状。