The DALTON program system is designed to allow convenient, automated determination of a large number of molecular properties based on an SCF, MP2 or MCSCF reference wave function. The program consists of four separate components, developed more or less independently. HERMIT is the integral generator, generating ordinary atomic and molecular integrals appearing in the time-independent, non-relativistic Schrödinger equation, as well as an extensive number of integrals related to different molecular properties. SIRIUS is the (MC)SCF wave function optimization part, and is described comprehensively in the METECC-94 book [1]. ABACUS evaluates the molecular properties of interest. RESPONSE is a general purpose program for evaluating response functions, up to cubic response functions for (MC)SCF wave functions and linear response for the Second-Order Polarization Propagator Approach (SOPPA).
Throughout this manual there will be references to articles describing the implementation of a specific molecular property or input option. This will hopefully suffice to give the reader a proper theoretical understanding of the current implementation. Only one reference otherwise not mentioned in the text, the treatment of symmetry , is given here [2].
DALTON is in many respects an ``expert's'' program. This is first noticeable in the range and selection of molecular properties that may be calculated. As described in the individual sections, the range of molecular properties, some of which are highly non-standard, is fairly large. On the other hand, several common properties can perhaps more easily be calculated using other, commercially available, quantum chemistry program packages.
We have tried when writing this manual to emphasize the modularity of the input, as well as indicating the advantages that may be obtained from the flexibility of the input. Yet, whether the authors of this manual have succeeded or not, is up to the reader to decide, and any comments and suggestions for improvements, both on the manual as well as the program, will be much welcome.