SIESTA 5.4.2 Release Notes (2025-12-16)

We are pleased to announce Siesta 5.4.2, the second point release of Siesta 5.4. Siesta 5.4.2 incorporates the following changes:

Changes and improvements

Removed the read_options dependency for the QMMM driver. This reduces the need of extra dependencies and dummy modules. Cleaned up pressure units from read_options. Removed now unnecessary dummy modules.

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Reworked the QMMM Ewald sums in order to avoid numerical issues.
- Added options to fine-tune each of the Ewald parameters (kcut-rcut-alpha).
- Several loops in pcpot and mmforces were rearranged.
- Ewald k-points are now pre-computed to save computational cost (at the cost of increased memory usage, but not much).
- In mmforces, the real-space mesh is precomputed to save time. This is only slightly detrimental in cases where there are too few MM atoms and too few Ewald k-points, so it should not happen in realistic cases.
- Separated the neutral-atom interaction. This is now done relying on Vna (from phiatm), and the Ewald part only includes the interaction against dRHO. This is much more stable and correct.
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Changed OpenMP threading option in MPI from ‘funneled’ to ‘serialized’
- Some pieces of code (e.g. the ELPA library) require the “Serialized” flavor.
- The change has been made both in Siesta and in TBtrans.
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Add interface for every MPI function call.

There were some MPI calls that were not using the proper interfaces. Some of them because they are not using mpi_siesta module and others not importing all required interfaces. This solve a bug in matel_table.F90 and matel_ylm.F90, where the implicit interface had problems dealing with MPI_IN_PLACE communications. This was producing execution errors when compiled with some compilers.

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Fixed p_atom variable initialization in kinefsm

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Added build flag for removing host-specific compilation options.

They are automatically removed when cross-compiling or when -DSIESTA_WITH_HOST_OPTIMIZATION=OFF.

(519)
Enhance external ELPA finder module. Use new ELSI official release v2.12.0

The ELSI upstream has incorporated (in v2.12.0) the relevant patches contributed by the Siesta project.

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Fix handling of OpenMP-enabled versions of ELPA

The new ELPA finder module uses the input variable ELPA_PREFER_OPENMP to search for the right flavor of ELPA. This variable is now set as a dependent option, which is hidden (and OFF) if SIESTA_WITH_OPENMP is OFF, and defaults to ON if SIESTA_WITH_OPENMP is ON (but can be set to OFF if desired).

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