# Software

## Quantum-chemistry program we are developing

The kernel of the Dalton2016 suite are two powerful molecular electronic structure programs, DALTON and LSDALTON. Together, the two programs provide an extensive functionality for the calculations of molecular properties at the HF, DFT, MCSCF, and CC levels of theory. Many of these properties are ONLY available in the Dalton2016 suite. The program is distributed free of charge after signing a license agreement.

Program for Atomic and Molecular Direct Iterative Relativistic All-electron Calculations.

The DIRAC program computes molecular properties using relativistic quantum chemical methods. The program is distributed free of charge after signing a license agreement.

Gen1Int is a Fortran 90 library (with Python interface) to evaluate the derivatives of one-electron integrals with respect to the geometry perturbation, external electric and magnetic fields, and total rotational angular momentum at zero fields with contracted rotational London atomic orbitals (LAO). The program is distributed free of charge under the Lesser Gnu Public License.

The Gauge-Including Magnetically Induced Currents (GIMIC) program calculates, visualizes and analyzes magnetically induced currents in molecules. The GIMIC code implements the theory outlined in ref. Jusélius J., Sundholm D. and Gauss J., Calculation of Current Densities using Gauge-Including Atomic Orbitals, J. Chem. Phys., 121 3952 (2004) (pdf). A more recent review on magnetically induced current densities highlighting GIMIC applications is given here. GIMIC is currently interfaced to CFOUR, Turbomole, QChem, Gaussian and LSDalton.

Re(lativistic) Spect(roscopy) program is a free, MPI parallelized computational chemistry program aimed at fast and reliable prediction of spectroscopic properties of closed- and open-shell molecules containing heavy elements. The molecular properties are accurately modeled with the full four-component Dirac-Coulomb (DC) Hamiltonian in order to include relativistic corrections variationally, and density functional theory (DFT) to account for correlation effects. The program also provides in-built all-electron basis sets suitable for relativistic calculations of all elements in the periodic table (Z=1-118), as well as several analysis and visualization tools.

TDRSP is a tool package solving the equation of motion of reduced single-electron density matrix in the framework of Hartree-Fock or density functional theory in time domain.

XCFun is a library of approximate exchange-correlation functionals, used in the Density Functional Theory description of electronic structure. Because XCFun is based on automatic differentiation the library can provide arbitrary order derivatives of all supported functionals. The program is distributed free of charge under the Lesser Gnu Public License.

MRChem (Multi-Resolution Chemistry) is a C++ code which makes use of Multiresolution analysis and Multiwavelets for Density Functional Theory. The code is capable of running restricted and unrestricted DFT calculations within any predefined accuracy with respect to the complete basis result, thus lifting the limitations of traditional atom-centered basis sets. MRChem is built upon a set of C++ libraries called MRCPP (Multiresolution Computational Program Package) which provide the mathematical tools and framework to solve the Kohn-Sham equations with Multiresolution analysis.

PCMSolver is a collection of libraries/modules which allow to add continuum solvation capabilities to any Quantum Chemistry (QC) code. The main idea is to be able to interface a generic QC code with PCMSolver by a minimal programming effort. The code is highly modular with a Python input parser and C++ overlay connecting the three main modules: (1) cavity generator, (1) Green's function generator and (3) Boundary Equation solver. Thanks to the object orientation paradigm, each module is present in different variants which can be selected depending on the problem at hand.

## Quantum-chemistry program we are contributing to

CFOUR (Coupled-Cluster techniques for Computational Chemistry) is a program package for performing high-level quantum chemical calculations on atoms and molecules. The major strength of the program suite is its rather sophisticated arsenal of high-level ab initio methods for the calculation of atomic and molecular properties. Virtually all approaches based on Møller-Plesset (MP) perturbation theory and the coupled-cluster approximation (CC) are available; most of these have complementary analytic derivative approaches within the package as well.

CRYSTAL is a general-purpose program for the study of crystalline solids, and the first which has been distributed publicly. The CRYSTAL program computes the electronic structure of periodic systems within Hartree Fock, density functional or various hybrid approximations. The Bloch functions of the periodic systems are expanded as linear combinations of atom centred Gaussian functions. Powerful screening techniques are used to exploit real space locality.

## Software being developed that are not yet released publicly

**OpenRSP**

An implementation of the density-matrix-based response theory approach of Thorvaldsen et al. (J.Chem.Phys. 121, 214108 (2008)) for time- and perturbation-dependent basis sets. Once completed, the module will supply molecular properties of arbitrary order and for an arbitrary perturbation operator, static or frequency-dependent, from a density matrix in the atomic orbital basis obtained in an SCF-based electronic structure model. The program will rely on the availability of modules that will solve the coupled-perturbed Hartree-Fock/Kohn-Sham equations, differentiated one- (and two-electron, if needed) integrals, as well as a routine for evaluation exchange-correlation kernels in the case of Kohn-Sham DFT.