APTS is a program written by Jun Zhang for performing accurate and efficient correlation calculations for large molecules by incremental scheme. In brief, APTS can decompose a large molecule into several fragments, perform the correlation calculation for each fragment and combine the results to produce the final total energy. The essential approach in APTS is called incN-db-B0 (Nth-order incremetal dual-basis set zero-buffer). With the help of APTS, one can perform very large calculations, say, CCSD(T) with 1000 basis functions, using ordinary hardware (like 50 CPU cores). Below are some of its characters:


When you use APTS in your work, I will appreciate you if you can cite the following publication:

If you use APTS to do F12 calculations or for open shell molecules, please cite the following publications:


APTS can only be run in Linux with Molpro. You must have Molpro with a valid license. Please contact Jun Zhang for this code.