I've got a question about interpreting these - mainly about how the horizontal axis works. See attached file - On the leftmost panel, it has a form of the wavevector q plotted from left to right, labeled as (000) on the left and (100) on the right. What does this mean? Does it mean that the wavevector, as you move from left to right, is always pointing in the (100) direction, and its magnitude simply increases? Or does the wavevector's direction change too? Any good resources for understanding these would be much appreciated!