I was tried to run an opt + freq calculation on water at NEVPT2/cc-pVDZ level of theory based on the tutorial for the CASSCF calculation in the Dalton manual using this input: ``` Content of the .dal input file ---------------------------------- **DALTON INPUT .OPTIMIZE **WAVE FUNCTIONS .HF .MP2 .MCSCF .NEVPT2 *SCF INPUT .DOUBLY OCCUPIED 3 1 1 0 *CONFIGURATION INPUT .SYMMETRY 1 .SPIN MULTIPLICITY 1 .INACTIVE 1 0 0 0 .CAS SPACE 4 2 2 0 .ELECTRONS 8 **START .SHIELD .MAGNET **PROPERTIES .DIPGRA .VIBANA **END OF DALTON INPUT Content of the .mol file ---------------------------- BASIS cc-pVDZ Water geometry optimisation: NEVPT2/cc-pVDZ Project - Optimisation Atomtypes=3 ZMAT O 1 8.0 H 2 1 0.9 1.0 H 3 1 0.9 2 100.0 1.0 ``` Unfortunately, I came across an error: ``` *************************************************************************************** ****************** Output from **INTEGRALS input processing (HERMIT) ****************** *************************************************************************************** - Using defaults, no **INTEGRALS input found Default print level: -1 Calculation of one-electron Hamiltonian integrals. Center of mass (bohr): 0.008880851323 0.000000000000 -0.026428720411 Operator center (bohr): 0.000000000000 0.000000000000 0.000000000000 Gauge origin (bohr): 0.008880851323 0.000000000000 -0.026428720411 Dipole origin (bohr): 0.008880851323 0.000000000000 -0.026428720411 --> ERROR (GPOPEN) TRYING TO USE A FILE NUMBER ALREADY IN USE --> Offending UNIT number: 12 --> Name of offending file (if any): MOTWOINT ### Please report the problem on http://daltonforum.org Input parameter status : UNKNOWN Input parameter access : Input parameter format : --> Name of file already opened for this unit: MOTWOINT QTRACE dump of internal trace stack ======================== level module ======================== 11 GPOPEN 10 HERCTL 9 HERMIT 8 GTNRGY 7 GTNPNT 6 NMDER 5 NUMDRV 4 RUNOPT 3 OPTMIN 2 DALTON 1 DALTON main ======================== --- SEVERE ERROR, PROGRAM WILL BE ABORTED --- Date and time (Linux) : Thu Feb 5 14:36:20 2026 Host name : augustus @ MPI MASTER, node no.: 0 @ Reason: ERROR (GPOPEN) TRYING TO OPEN A FILE ALREADY IN USE Total CPU time used in DALTON: 10 minutes 33 seconds Total wall time used in DALTON: 2 minutes 42 seconds ``` As you can see, the output asks me to report the problem here, so this is what I am doing. I'm not quite sure what the problem is, and I'm not even sure if the final energy/geometry was genuinely optimised using NEVPT2 or just CASSCF. The full output should be attached below. If anyone can help me out with this, I would appreciate it. I'm completely new to Dalton, so I don't have any idea how to debug the problem myself. [h2o-opt-nevpt2-dz.out](/uploads/f56851f6e08e071e1af1584f8282a525/h2o-opt-nevpt2-dz.out)