Elk version 9.1.15 released

Dear All,

Elk version 9.1.15 has just been released.

New features include the piezoelectric and magnetoelectric tensors. This are calculated using the Berry phase method of R. D. King-Smith and David Vanderbilt, Phys. Rev. B 47, 1651(R) (1993). See the examples in the elk/examples/piezoelectric and elk/examples/magnetoelectric directories for details.

We've also updated the code to enable exchange-correlation functionals with Laplacian terms. This is useful some types of meta-GGAs, including those which are 'de-orbitalised' using the method of D. Mejia-Rodriguez and S. B. Trickey, Phys. Rev. B 98, 115161 (2018). Partial de-orbitalisation has also been improved and now works with the complete range of kinetic energy density functionals in Libxc; see arXiv:2304.02363.

The change of large parts of the code to single-precision arithmetic has been completed. This includes Hartree-Fock, hybrid functionals, RDMFT, OEP, GW and the linear-response functions. All these methods are now considerably faster and more memory efficient as a result.

Finally, Elk has been recognized with a Community Leader Award by SourceForge; thanks to all the users and contributors for making the code as useful as it is, as well as for making the forums a congenial place for everyone.

Best wishes,
Kay Dewhurst, Sangeeta Sharma, Lars Nordström, Francesco Cricchio, Oscar Grånäs and Hardy Gross.

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elk-9.1.15
-added piezoelectric and magnetoelectric tensors as tasks 380 and 390, respectively; see the examples for details; these are currently experimental features
-exchange-correlation functionals with Laplacian terms now working; this includes the deorbitalised functionals of Mejia-Rodriguez and Trickey, Phys. Rev. B 98, 115161 (2018)
-improved the meta-GGA partial deorbitalisation: it now works with the complete range of kinetic energy density functionals in Libxc (see arXiv:2304.02363)
-improved the interface to Libxc
-removed potential-only meta-GGA functionals
-time-dependent Kohn-Sham states are now orthogonlised using a singular value decomposition every 'ntsorth' time-steps in order to improve stability; the default is 1000 time-steps
-new task 485 outputs the Fourier transform of the time-dependent total current J(ω)
-new input variable 'jtconst0' will, when set to .true., zero the constant part of J(t) before the dielectric function is calculated with tasks 480 and 481
-changed large parts of the code to single-precision arithmetic including Hartree-Fock, RDMFT, OEP, GW and the linear-response functions; as a consequence the code is considerably faster
-changed relational operator symbols such as .le., .gt., etc. to '<=', '>', etc. in line with modern Fortran style
-increased maximum allowed number of files on the RAM disk to 32
-many optimisations and minor bug fixes
-added more and improved existing OpenMP parallelism