CRYSTAL09 new features at a glance

CRYSTAL09 is a major release and the most relevant new features are:


Static polarizability and dielectric tensor through a Coupled Perturbed HF/KS scheme

The static polarizability of crystalline systems, the dielectric tensor, the refractive indices, the birifrangence and optical axes (all these quantities can be obtained from the first one) are computed through a new implementation of the CPHF(KS) scheme. A tutorial (High frequency dielectric constants by CPHF(KS)) is available on how to use this new feature.

Alternatively, a saw-tooth finite-field scheme can be applied to the periodic system; A tutorial (High frequency dielectric constants by FIELD) is also available for this option.
Limits and merits of this approach with respect to CPHF(KS) are illustrated.

References
M. Ferrero, M. Rérat, R. Orlando, R. Dovesi Coupled perturbed Hartree-Fock for periodic systems: the role of symmetry and related computational aspects J. Chem. Phys. 128, 014110 (2008)
M. Ferrero, M. Rérat, P. Orlando, R. Dovesi The calculation of static polarizabilities of periodic compounds. The implementation in the CRYSTAL code for 1D, 2D and 3D systems J. Comput. Chem. 29, 1450-1459 (2008)
M. Ferrero, M. Rérat, B. Kirtman, R. Dovesi Calculation of first and second static hyperpolarizabilities of one- to three-dimensional periodic compounds. Implementation in the CRYSTAL code J. Chem. Phys. 129, 244110 (2008)


Phonon dispersion using a direct approach and infrared intensities through a Berry phase approach

Phonon dispersion using a direct approach

The calculation of phonon frequencies at k points different form Gamma is now possible. This enables a more accurate calculation of the thermodynamic properties and the comparison of calculated frequencies with experimental Inelastic Neutron Scattering (INS) spectra. The scheme is based on a direct approach which implies the calculation of the Hessian matrix on supercells. An efficient exploitation of symmetry helps the reduction of computational cost, by finding the irreducible set of atomic displacements compatible with the supercell. A new section has been added to the “Vibrational Frequencies Calculation” tutorial to explain the new keywords.

Infrared intensities through a Berry phase approach

A new scheme to compute IR intensities has heen implemented based on a Berry phase approach. This scheme parallels the localized Wannier-based one to which it offers a cost effective alternative.


Transition state search

Several tools that allow molecules, polymers, slabs and crystals to be optimized in valence coordinates as well as a suitable saddle point optimization technique to search for transition state structures for this kind of systems have been implemented.
The adoption of these localized coordinate systems largely facilitates the study of chemical processes in periodic systems with atomic connectivity, as occurs in catalytic reactions on zeolites, clathrates or oxidic surfaces.
The new features have been illustrated to study the proton jump between oxygen atoms of the Brønsted site in the H-chabazite zeolite.

A tutorial is also available on how to use these new features

References
A. Rimola, C. M. Zicovich-Wilson, R. Dovesi, P. Ugliengo The distinguished reaction coordinate method: search and characterization of transition state structures in crystalline systems using the periodic CRYSTAL program J. Chem. Theory Comput. 6 (2010) 1341


Constant pressure geometry optimization of cell constants and atomic positions

The calculation of the stress tensor and related properties have been implemented in the CRYSTAL code. The stress tensor is obtained from analytical gradients with respect to the cell parameters. The pressure and the enthalpy are then computed. The possibility of applying external pressure has also been implemented.
The constant-pressure optimization offers an alternative optimization method in addition to the already implemented optimization at constant volume.

References
K. Doll Analytical stress tensor and pressure calculations with the CRYSTAL code Mol. Phys. (2010) (DOI: 10.1080/00268970903193028)


Automated calculation of the elastic tensor of crystalline systems

An automated procedure for calculating second-order elastic constants for crystalline systems of any symmetry has been implemented. Second derivatives with respect to strain are evaluated numerically from analytical gradients. The internal co-ordinates are re-optimized with each applied strain. Point group symmetry is exploited to reduce the number of needed deformations according to Laue’s classes.

References
W.F. Perger, J. Cryswell, B. Civalleri and R. Dovesi Ab initio calculation of elastic constants of cristalline systems with the CRYSTAL code Comput. Phys. Commun. 180, 1753-1759 (2009)


Automated E vs V calculation for equation of state

E vs V curves can now be computed automatically by just specifying a range of volumes. A constant volume geometry optimization is perfomed for each point and then results are fitted to most common equation of states and polynomial.
Work is in progress to extend this scheme to E vs P calculations.


New DFT methods

New GGA functionals for solids

The set of available GGA functionals in CRYSTAL has been extended to include the newly developed GGA functionals for solids, namely: the PBEsol one [1] for exchange and correlation, the exchange Wu-Cohen functional [2] and the exchange SOGGA of Zhao-Truhlar [3]. Also, the Wilson-Levy correlation functional [4] has been added.
Old and new functionals have recently been tested for different solids [5-7]

References
[1] J. P. Perdew, A. Ruzsinsky, G. I. Csonka, O. A. Vydrov, G. E. Scuseria, L. A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett. 100 (2008) 136406
[2] Z. Wu, R. Cohen, Phys. Rev. B 73 (2006) 235116
[3] Y. Zhao, D. G. Truhlar J. Chem. Phys. 128 (2008) 184109
[4] L. C. Wilson, M. Levy, Phys. Rev. B 41 (1990) 12930
[5] R. Demichelis, B. Civalleri, M. Ferrabone, R. Dovesi, Int. J. Quantum Chem. 110 (2010) 406
[6] D. I. Bilc, R. Orlando, G. M. Rignanese, J. Iniguez, P. Ghosez, Phys. Rev. B 77 (2008) 165107
[7] B. Civalleri, D. Middlemiss, R. Orlando, C. Wilson, P. Ugliengo, Chem. Phys. Lett. 451 (2008) 287

London-type empirical correction for dispersion interactions

An empirical correction term to include dispersion interactions in DFT methods as proposed by Stefan Grimme [1] is available. It is a damped pairwise London-type term of the form -s6fdmpC6/R6. The correction is applied to the computed ab initio total energy and gradients. Therefore, total energy calculation, geometry optimization and vibrational frequency calculation can be carried out by including the empirical dispersion correction.
The current implementation has been mainly tested and used in combination with the B3LYP method with application to molecular crystals and layered materials [2,3].

References
[1] S. Grimme, J. Comput. Chem., 2006, 27, 1787
[2] B. Civalleri, C.M. Zicovich-Wilson, L. Valenzano, P. Ugliengo, CrystEngComm, 2008, 10, 405; 1693(E)
[3] P. Ugliengo, C.M. Zicovich-Wilson, S. Tosoni, B. Civalleri, J. Mater. Chem., 2009, 19, 2564


New tools to build 1D structures

Three different options are now available for the creation of 1D structures, namely: Symmetry is fully exploited, so that calculations involving hundreds of atoms using good-quality basis sets and hybrid HF/DFT functionals are feasible at a relatively low cost. The present limit for the roto-translation group is now 48 operators; this limit is going to disappear in the next few months.

Automatic generation of nanotubes from single-layer systems

New options were implemented in the CRYSTAL code, which permit in a relatively easy way to generate 1D nanotubes starting from 2D structures, or by cutting a slab from a 3D bulk and then roll it up into a tube. This strategy allows users to exploit the full roto-translational symmetry of nanotubes (helical groups) and to drastically reduce the computational costs [1]. A tutorial (--> Nanotube systems) shows how to prepare a basic input, describes the related options, how to re-use the optimized geometry for a given (N1,N2) tube as a starting point for a new (N1',N2') tube and so on. Relevant references on recent applications (carbon nanotubes, inorganic tubes such as imogolite and chrysotile [1,2]), examples, graphical demonstrations and exercices are also provided.

References
[1] Y. Noel, Ph. D'Arco, R. Demichelis, C.M. Zicovich-Wilson and R. Dovesi On the use of symmetry in the ab initio quantum mechanical simulation of nanotubes and related materials J. Comput. Chem. 31 (2010) 855
[2] Ph. D'Arco, Y. Noel, R. Demichelis, R. Dovesi Single-layered chrysotile nanotubes: A quantum mechanical ab initio simulation J. Chem. Phys. 131 (2009) 204701

Helical symmetry for polymers

Helical polymers can now be modelled by fully exploiting the roto-translational symmetry of the helix (up to order 48).
This has been recently applied to investigate the conformational behavior of polyglycine helical infinite chains.

References
A. M. Ferrari, B. Civalleri, R. Dovesi Ab initio periodic study of the conformational behavior of glycine helical homopeptides J. Comput. Chem. 31 (2010) 1777 [DOI:10.1002/jcc.21468]


New tools for initial guess of SCF for d- and f-partly occupied atoms

A new option has been inserted that permits to define the occupation of specific f or d orbitals in a given shell for open shell systems. Electrons belonging to partially filled shells can then be assigned to selected AOs.
This allows user to have a better control of the initial guess and an easier convergence for the SCF process.


New tools treatment of solid solutions

A new option permits to investigate solid solutions through the following steps:
  1. select an appropriate supercell of the system: the dimension must be adequate to describe the kind of disorder you are interested in;
  2. define the number of Y atoms to be substituted: the symmetry independent configurations are listed automatically by the code;
  3. optimize the structure of a few configurations (quantum mechanical calculations for each configuration);
  4. define a TWO-BODY model (TBM) involving neighbours up to a given distance;
  5. define by best-fit the parameters of the TBM;
  6. compute with the TBM the energy of all the symmetry independent configurations, and order them by energy;
  7. restart from point (3) adding new configurations to the list of the fully optimized ones;
  8. when the list in (7) proposes already explored configurations as the most stable, and when the parameters of the model are stable with respect to the number of data in the fitting, perform the statistical mechanics final calculations.
A tutorial with more information and examples is available.

References
A. Meyer, P. D'Arco, R. Orlando, R. Dovesi, J. Phys. Chem. C 113 (2009) 14507
A. Meyer, P. D'Arco, R. Orlando, C. M. Zicovich-Wilson, L. Maschio, R. Dovesi, J. Chem. Phys. submitted


Revised implementation of Electron Momentum Density analysis and Compton profiles

The CRYSTAL program allows the accurate determination of the one-electron Density Matrix (DM) of crystalline systems, both at Hartree-Fock level and within the Density Functional Theory; Since the earlier public versions of the program, many DM-related quantities, both in direct and momenta space, can be easily evaluated.

The majority of the algorithms which concern these properties has been improved in the CRYSTAL09 version of the program and new algorithms have been implemented; in particular:

A tutorial (EMD) with more information and examples is available.

References
A. Erba, C. Pisani, S. Casassa, L. Maschio, M. Schutz, D. Usvyat, Phys. Rev. B 81 (2010) 165108


Enhanced Massive-parallel version (MPPcrystal - distributed memory)

An enhanced Massive parallel version of the code is available that allows user to reach an improved scaling in parallel execution on super-computing resources for very large systems.
Here is an example of the scaling of the code with the number of processors up to 1024 cores.

Note: MPPcrystal does not implement: (i) IR intensities calculation and (ii) coupled perturbed CPHF/CPKS scheme

References
P. Ugliengo, M. Sodupe, F. Musso, I.J. Bush, R. Orlando, R. Dovesi
Realistic Models of Hydroxylated Amorphous Silica Surfaces and MCM-41 Mesoporous Material Simulated by Large-scale Periodic B3LYP Calculations
Adv. Mater. 20 (2008) 4579