Metals: Automatic k-point generation for a 60% speed-up of total energy calculations

A generalized regular k-point grid generation method (more general than the traditional Monkhorst-Pack method) leads to a 60% speed-up for total energy calculations of metallic systems. Generalized regular grids can be generated using the JHU kpoint server: http://muellergroup.jhu.edu/K-Points.html. We have developed a new algorithm that can generate these same grids on the fly so that a web request is not necessary. The algorithm relies on group theoretical ideas that connect the concepts of lattices and integer matrices to yield extremely fast grid generation, enabling scans over thousands of candidate grids and select one with the highest efficiency (best k-point symmetry reduction).