# ORCA Version 4.1 released

17 12 18 - Filed in: computational chemistry

With the release of ORCA 4.1, they have moved our forum and download site to a new server at the Max Planck Institute fuer Kohlenforschung, where the ORCA team now has its home base. Now at https://orcaforum.kofo.mpg.de.

ORCAis an ab initio quantum chemistry program package that contains modern electronic structure methods including density functional theory, many-body perturbation, coupled cluster, multireference methods, and semi-empirical quantum chemistry methods. Its main field of application is larger molecules, transition metal complexes, and their spectroscopic properties. DOI.

List of new features for ORCA 4.1:

SCF/DFT

- B97M-V, wB97M-V, wB97X-V plus various D3 variants of B97 functionals
- Simple input keywords for DSD-BLYP, DSD-PBEP86, and DSD-PBEB95
- CPCM analytic Hessian
- DLPNO-double hybrid DFT including gradient
- SymRelax option in %method

Semiempirical methods

- XTB method of Grimme et al.

Coupled cluster

- Iterative solution of the full (T) equations for DLPNO-CCSD(T)
- Open shell DLPNO-CCSD density and spin density matrices
- Full DLPNO-MP2 gradient
- CIM (Cluster in molecules) Implementation with MP2, CCSD(T), DLPNO-MP2 and DLPNO-CCSD(T)
- IP and EA coupled cluster methods and their DLPNO variants
- STEOM-CCSD for open shells
- SOC between bt-PNO-STEOM and STEOM states
- Improved Multilevel implementation including multilevel DLPNO-IP
- F12-Triples scaling for RHF canonical CCSD(T) based on the CCSD/ CCSD-F12 ratio

Multireference

- New CASSCF SuperCIPT converger is reliable and efficient.
- New options for final orbitals to find partner orbitals for the chosen active space e.g. bonding / anti-bonding partners.
- MC-RPA (Multiconfigurational random phase approximation)
- ◦ AO driven integral direct for calculations on larger molecules
- ◦ Fock matrix -> conventional, direct, RIJ/COSX
- ◦ MPI parallel
- ◦ NTOs for visualizing transitions
- Checking stability of state specific CASSCF wave functions by orca_mcrpa
- Dynamic correlation dressed (DCD-CAS) method with inclusion of relativistic effects (SOC, spin-spin, magnetic fields)
- CASSCF RIJCOSX allows two separate auxiliary basis sets
- CASCI/NEVPT2 protocol for XAS and RIXS

Optimization

- Nudge elastic band method to locate transition states
- Enabled 3-dimensional relaxed potential energy surface scan
- Improvement of redundandant internal coordinate generation
- Faster and more smooth convergence for 3-dimensional systems and embedded cluster models
- Intrinsic reaction coordinate (IRC) following
- Swart model Hessian (good for weak interactions)

Molecular Dynamics

- MD simulations can now use Cartesian, distance, angle, and dihedral angle constraints.
- The MD module now features cells of several geometries (cube, orthorhombic, parallelepiped, sphere, ellipsoid), which can help to keep the system inside of a well-defined volume.
- The cells can be defined as elastic, such that their size adapts to the system. This enables to run simulations under constant pressure.
- Ability to define regions (subsets of atoms) enables applications such as thermostating different parts of the system to different temperatures (cold solute in hot solvent, temperature gradients, ...)
- Trajectories can now be written in XYZ and PDF file format.
- A restart file is written in every simulation step. Simulations can be restarted to seamlessly continue.
- The energy drift of the simulation is now displayed in every step.
- The MD module now works with a broader range of methods (semiempirics, ECPs, QM/MM).
- Fixed a bug in the time integration of the equations of motion which compromised energy conservation.

Spectroscopic properties

- orca_pnmr module tool to calculate paramagnetic NMR spectra
- NMR chemical shifts with RI-MP2 and double hybrid DFT including GIAO’s, spin-component scaling and CPCM
- NMR Spin-Spin coupling in calculations with DFT/HF
- NMR wth ZORA
- Maximoff-Scuseria correction for the kinetic energy density in GIAO-based calculations with meta-GGA functionals
- Exact and gauge invariant transition moments and approximate decomposition into dipole, quadrupole etc terms in all modules.
- PNO-ROCIS method for more efficient X-ray absorption calculations
- IP-ROCISD for high spin ROHF references
- TD-DFT:
- Transient spectra (excited state absorption) for CIS/TDA
- Triplet gradients (with RIJ, COSX and all) for all cases.
- Spin orbit coupling (including CPCM) and gradients
- Root following scheme for optimization
- Slow term to correct energy of relaxed excited state
- Full TD-DFT with double hybrids
- ESD module to calculate spectroscopic properties
- Vibrationally resolved absorption spectra including Duschinsky rotation and/or vibronic coupling.
- Fluorescence and Phosphorescence rates with same options.
- Resonance Raman spectra with the same options
- works with CIS/TDDFT, ROCIS, CASSCF and EOM/STEOM.
- Seven different schemes for obtaining an excited state PES and five different choices of coordinate systems

Analysis tools:

- Open Shell LED
- Dispersion interaction Density plots
- LED for DLPNO-MP2
- LED for the frozen state
- Update of AIM interface
- NBO 7 compatibility (i4)
- Miscellaneous
- Compound method (Infrastructure, plus W2.2, W1, G2(MP2), G2(MP2-SVP), G2(MP2-SV) methods)
- Property file (additional properties, plus new infrastructure)
- Decomposition of correlation energy for canonical RHF CCSD energies to singlet - triple pairs
- Additional EP2 extrapolation schemes using RI-MP2 and DLPNO-MP2 methods as cheap methods (request from forum)
- Lanthanide new def2 basis sets
- def2-XVP/C auxiliary basis sets for Ce-Lu by Chmela and Harding.
- Robust Second order optimizer for localized orbitals
- Added a few basis sets.

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