Hi all

I run the geometry optimization to the periodic structure which contains a vaccum slab and several layers of mineral , the dimension of lattice (a,b,c) changed after that, c is reduced to about half of the original value, does anyone know why that happened? Is there any influence on the following dynamic simulation? If I fix the lattice lengths, can the structure still be optimized? What's the difference between a fix-length-lattice optimization and non-fix-length-lattice optimization?

Thank you

Regards

Jing