By default, and in all examples shown so far, scratch files are used to store all intermediate data MOLPRO needs, and the user will normally not see these files at all. However, it is possible to save computed data as orbitals and energies in named (permanent) files and use these for restarting a calculation at a later stage. MOLPRO uses a number of different files, but only one or two of them are needed for a restart. File 1 holds the one- and two electron integrals and related information, while on file 2 the wavefunction information like orbitals, orbital energies, and optionally CI-vectors are stored. Thus, file 2 is essential for restarting a calculation, while the integrals on file 1 can either be restarted or recomputed.
The use of named files can be requested using the file directive, which should be given immediately after the memory command (if present), e.g.,
***,title memory,16,m !allocate 16 MW of memory file,1,filename.int !allocate permanent integral file file,2,filename.wfu !allocate permanent wave-function (dump) file geometry=... !define the nuclear coordinates basis=vdz !Select basis set hf !Perform HF calculation ccsd(t) !Perform ccsd(t) calculation
If the same files are used in a subsequent calculation, MOLPRO will automatically recover all data saved on the given files. For instance, if the following input is used after the previous example, the integrals and orbitals will be restarted and used for the subsequent casscf and MRCI calculations:
***,title memory,16,m !allocate 16 MW of memory file,1,filename.int !allocate permanent integral file file,2,filename.wfu !allocate permanent wave-function (dump) file casscf !casscf, using previous scf orbitals as starting guess mrci !mrci using casscf reference wavefunction
If only file 2 is defined in the input, the integrals will automatically be recomputed, as in the following input. Note that in most cases, file 1 can be very large (it contains the two-electron integrals), and the cost of recomputing the integrals can be a small fraction of the overall time; it is therefore usually sensible in this way to avoid declaring the file as permanent.
***,title memory,16,m !allocate 16 MW of memory file,2,filename.wfu !allocate permanent wave-function (dump) file casscf !casscf, using previous hf orbitals as starting guess mrci !mrci using casscf reference wavefunction
The automatic restart mechanism can be disabled by specifying new after the filename(s), e.g.,
***,title memory,16,m !allocate 16 MW of memory file,2,filename.wfu,new !allocate a new permanent wave-function (dump) file. !If the file exists, overwrite it. hf !Perform hartree-Fock calculation casscf !casscf, using hf orbitals as starting guess
Note that if permanent files are used, it is important to take care
that two simultaneous jobs do not attempt to use the same file!
molpro@molpro.net 2012-02-11