I read this book (pretty sure it was a novel and not just a short story) maybe 10-12 years ago. All I really remember about this book is part of the ending, but I think what I do remember is so specific that it should be easy if you know the book I'm looking for.
There was a group of children who had either mutated or evolved into being much smarter than the usual Homo sapiens. They were being kept in a space station, possibly by government/military, to keep them away from "regular" humanity. Towards the end, the kids - who seemed to be able to cooperate almost telepathically and had little interest in the humans caring for them - had built a device out of seemingly innocuous parts and captured a Strangelet.
It was very hard science fiction, and I thought it might have been by either Greg Bear or Stephen Baxter, but none of the book summaries by either one sound familiar, unless I'm just missing the right one, or these details have been left out of the summaries I've found.