(sec:general)= # General Information (sec:programs.general)= ## Program Components The program system ORCA consists of several separate programs that call each other during a run. The following basic modules are included in this release (listed in alphabetical order): :::{list-table} * - orca - Main input+driver program * - orca_ailft - Ab Initio Ligand Field Theory * - orca_autoci - CI type program using the automated generation environment (ORCA-AGE) * - orca_casscf - Main program for CASSCF driver * - orca_casscfresp - CASSCF static linear response * - orca_cclib - Precalculation of one particle coupling coefficients for ACCCI * - orca_ciprep - Preparation of data for MRCI calculations (frozen core matrices and the like) * - orca_cipsi - Iterative Configuration Expansion Configuration Interaction (ICE-CI) * - orca_cis - Excited states via CIS and TD-DFT * - orca_crystalprep - Set up an embedding calculation from a crystal structure file * - orca_eca - Auxiliary program for solving magnetic model Hamiltonians * - orca_esd - Excited state dynamics program for calculating vibronic spectra, resonance Raman, ... * - orca_guess - Generation of an intial guess for SCF and CASSCF * - orca_leanscf - Self consistent field program for HF and DFT * - orca_lft - Ligand Field Theory * - orca_loc - Calculation of localized molecular orbitals * - orca_mcrpa - CASSCF linear response for excited states * - orca_md - Molecular dynamics program * - orca_mdci - Matrix driven correlation program: CI, CEPA, CPF, QCISD, CCSD(T) * - orca_mp2 - MP2 program (conventional, direct and RI) * - orca_mrci - MRCI and MRPT calculations (individually selecting) * - orca_ndoint - Calculates semiempirical integrals and gradients * - orca_nmrspectrum - Simulates NMR spectra from calculated NMR parameters * - orca_numfreq - Numerical Hessian computation * - orca_pc - Addition of point charge terms to the one-electron matrix * - orca_plot - Generation of orbital and density plots * - orca_pop - External program for population analysis on a given density * - orca_prop - Calculation of molecular properties * - orca_propint - Calculation of property integrals * - orca_rel - (Quasi) Relativistic corrections * - orca_rocis - Excited states via the ROCIS method * - orca_scfgrad - Analytic derivatives of SCF energies (HF and DFT) * - orca_scfresp - self consistent field response * - orca_startup - Calculation of startup data before each single point * - orca_vpot - Calculation of the electrostatic potential on a given molecular surface * - orca_vpt2 - VPT2 analysis ::: Utility programs: :::{tabularcolumns} \Y{0.20}\Y{0.80} ::: :::{list-table} * - orca_2aim - Produces WFN and WFX files suitable for AIM analysis * - orca_2json - Converts information from the gbw-file into JSON files * - orca_2mkl - Produces an ASCII file to be read by molekel, molden or other visualization programs * - orca_asa - Calculation of absorption, fluorescence and resonance Raman spectra * - orca_chelpg - Electrostatic potential derived charges * - orca_euler - Calculate Euler angles from `.property.txt` file * - orca_exportbasis - Prints out any basis set in ORCA or GAMESS-US format * - orca_fitpes - Simple program to fit potential energy curves of diatomics * - orca_mapspc - Produces files for transfer into plotting programs * - orca_mergefrag - Merges MO coefficients from two independent .gbw files * - orca_pltvib - Produces files for the animation of vibrations * - orca_pnmr - Calculation of paramagnetic NMR shielding tensors * - orca_vib - Calculation of vibrational frequencies from a completed frequency run (also used for isotope shift calculations) * - otool_gcp - Geometrical Counterpoise Correction * - otool_xtb - For this release, xtb 6.7.1 needs to be downloaded from the [Grimme lab](https://github.com/grimme-lab/xtb/releases/tag/v6.7.1) ::: Friends of ORCA: :::{tabularcolumns} \Y{0.20}\Y{0.80} ::: :::{list-table} * - gennbo - The NBO analysis package of Weinhold (must be purchased separately from the university of Wisconsin; older versions available for free on the internet may also work) * - Molekel - Molecular visualization program (see {ref}`sec:plots.surface.molekel.detailed`) * - gOpenMol - Molecular visualization program (see {ref}`sec:plots.surface.gopenmol.detailed`) * - Avogadro - Molecular builder and visualization program with ORCA support (see [download page](https://orcaforum.kofo.mpg.de/app.php/dlext/) and [original repository](http://avogadro.cc)) * - Chemcraft - Molecular builder and visualization program with ORCA support (see [download page](https://www.chemcraftprog.com/)) * - SEQCROW - Molecular builder and visualization program with ORCA support (see [repository](https://github.com/QChASM/SEQCROW)) ::: In principle every individual module can also be called "standalone". However, it is most convenient to do everything via the main module. There is no real installation procedure. Just copy the executables wherever you want them to be and make sure that your path variable contains a reference to the directory where you copied the files. This is important to make sure that the programs can call each other (but you can also tell the main program the explicit position of the other programs in the input file as described below). The xtb tool (recommended version 6.7.1 or higher) needs to be downloaded separately from the [Grimme lab's repository](https://github.com/grimme-lab/xtb/releases/tag/v6.7.1). The xtb binary needs to be copied to the directory to which the orca binaries were copied to. (sec:units.general)= ## Units and Conversion Factors Internally the program uses atomic units. This means that the unit of energy is the Hartree (Eh) and the unit of length is the Bohr radius ($a_0$). The following conversion factors to other units are used: :::{list-table} * - 1 Eh - = - 27.2113834 eV - * - 1 eV - = - 8065.54477 cm$^{-1}$ - = 23.0605 $\frac{\text{kcal} }{\text{mol} }$ * - 1 cm$^{-1}$ - = - 29979.2458 MHz - * - 1 $a_0$ - = - 0.5291772083 Å - * - 1 a.t.u. - = - 2.4188843 10$^{-17}$ s - :::