SCM’s periodic density functional theory program, BAND, has undergone significant efficiency increases since its release in the fall of last year. Computer programmers and users know that disk speed is slower than RAM speed and as such programs that limit access to disk can function more quickly as a result. Two ways of doing this are by limiting the size of stored data sets by not including any unnecessary degree of precision, and by simply re-computing data sets that can be discarded and re-created faster than they can be written and read. The latest upgrades to the BAND program employ both of these time saving techniques. The improvement can be seen in the example jobs below:
The crystalline system on the left is YBa2Cu3O7. For a sample job the time to complete one SCF cycle dropped from approximately 1 hour and 50 minutes to only 15 minutes when run on a desktop computer running the Windows 7 operating system with a quad-core 2.67GHz Intel Xenon processor and 4GB of RAM. In the slower calculation the load on the processor cores repeatedly drops while the program waits for disk access, whereas in the faster calculation with the new default parameters for the development version of BAND, all 4 cores of the processor remain at full load during this part of the calculation. The same results are produced in each calculation.
Note that these changes are currently available in the development snapshots of our programs, which can be downloaded at http://www.scm.com/SCMForms/DownloadSnapshots.jsp.