I can not find any mistake in your calculations. Maybe you can use a
different base. But, how do you know that the correct angle is 96^o and
not 99^o ? Is this difference very important for you? I mean several
theoretical approaches may have some differences with respect to the
experiment, but they sill can be used to derive useful results.


> Dear Siesta users,
> I'm trying to perform the optimization of an unit cell composed by four
> molecules of the a neurotransmitter (for reference, the type of system is
> similar to: J. Appl. Phys. 129, 234702 (2021);
> https://urldefense.com/v3/__https://doi.org/10.1063/5.0054383__;!!D9dNQwwGXtA!VFwPgy7nicqJ4IHnnPgVwKcU8-H_FqWGOqP4Sbhw1XjlP5vvlaNC3lgewdXOsPI0ygo0IQ2_Io4V3TxayhNCrw$
> ). It's a monoclinic crystal with equal alpha and gamma angles. 
> When I run the geometry optimization, the result is always the shortening
> of the a, b, c, alpha and gamma, and the increase of beta (from 96° to
> 98-99°). However, it is expected that the a, b, and c parameters to
> increase. I thought it could be something related with the
> pseudopotencial, and downloaded the PBE Pseudopotencial from different
> sources, but nothing change. 
> Could someone help me to understand what's wrong? 
> I'm including the parameters I used to control the simulation
> #MD.TypeOfRun           CG               MD.Steps                   
>  2000            MD.MaxDispl               0.001 Bohr      MD.MaxForceTol 
>        0.01 eV/Ang      MD.VariableCell         T             
>   MD.MaxStressTol        0.02 GPa         MD.TargetPressure      0.0 GPa 
>         
> # WriteCoorStep           TWriteForces             TWriteMDHistory       
>   TWriteCoorInitial        T
> # DM.UseSaveDM            TMD.UseSaveXV            TMD.UseSaveCG         
>   T
> Thank you for your help
> --
> SIESTA is supported by the Spanish Research Agency (AEI) and by the
> European H2020 MaX Centre of Excellence 
> (https://urldefense.com/v3/__http://www.max-centre.eu/__;!!D9dNQwwGXtA!UqJJRS4uVg7t-Dbd_eAjfVnwWZ1t2C6FcN2aIQ3zMnpwP4Ll9vMlgtpcq4qP80YzOBfKsToR3FKvor_wWQ0$
>  )
>


*********************************************************
Dr Zacharias G. Fthenakis
**********************************************************

-- 
SIESTA is supported by the Spanish Research Agency (AEI) and by the European 
H2020 MaX Centre of Excellence (http://www.max-centre.eu/)

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