mecp_2.md

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default	MECP Screening	MECP Calculations	Examples and Guides	2	false	(Semi-automated) Screening of benzene MECPs with GFN2-xTB	/page/examples/mecp/mecp_screen.html

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CREST 3.0

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(Semi-automated) Screening of benzene MECPs with GFN2-xTB

An extension of the minimum energy crossing point optimization, is the metadynamics-based screening (analogously to conformational sampling). It can be called via the new input file reader {{site.data.icons.book}}. Again, for the GFN2-xTB S₀/T₁ MECPs of benzene: {: .text-justify }

{{ site.data.icons.code }} command {{ site.data.icons.codefile }} struc.xyz {{ site.data. icons.codefile }} input.toml

{% include command.html cmd="crest --input input.toml" %}

{% capture struc_file %} 12

C 1.3830400000 -0.2213700000 0.0054100000 C 0.8812100000 1.0799600000 0.0137400000 C -0.4965300000 1.2961400000 0.0106300000 C -1.3728900000 0.2109800000 -0.0044700000 C -0.8710300000 -1.0904600000 -0.0146100000 C 0.5067700000 -1.3067000000 -0.0079300000 H 2.4566500000 -0.3899700000 0.0090900000 H 1.5639800000 1.9254500000 0.0228700000 H -0.8876100000 2.3099700000 0.0197800000 H -2.4463500000 0.3796100000 -0.0082500000 H -1.5536800000 -1.9359000000 -0.0272900000 H 0.8977800000 -2.3206600000 -0.0132700000 {% endcapture %} {% include codecell.html content=struc_file style="font-size:10px" %}

{% capture toml_file %} #This is a CREST input file input = 'struc.xyz' runtype='mecp_search' # MECP sampling runtype

#parallelization threads = 10

#calculation data [calculation] eprint = true elog="energies.log"

[[calculation.mecp]] # This block automatically sets up a uhf=0 and uhf=2 calculation with xtb method = "xtb" binary = "xtb" flags = "--gfn 2 --grad"

[[calculation.constraints]] gapdiff2 = [7.5, 0.005, 0.25]

#molecular dynamics data, required for MECP sampling runtype [dynamics] length = 10.0 tstep = 2.5 dump = 100.0 hmass = 4

{% endcapture %} {% include codecell.html content=toml_file style="font-size:10px" %}

{% include defaulttab.html id="open-1" %}

The sampling algorithm will run in parallel several (i.e., ten) metadynamics simulations on the mixed PES including the gap potential and MECP-optimize the output trajectories. While the metadynamics bias potentials are set up automatically, the user is responsible for setting the MD parameters, such as the simulation lengths in ps. Some benzene MECPs that can be found with this method are shown below (in comparison with FOMO-CASCI(6,5) structures in transparent blue). {: .text-justify }

{% include image.html file="example-mecp-2.png" alt="Benzene MECPs" caption="Some GFN2-xTB S₀/T₁ MECPs for benzene, found with semi-automated metadynamics sampling. Transparent blue are FOMO-CASCI(6,5) reference structures." max-width=700%}