# 4.6. Example: HNO3(H2O)10 in Electric Field

Tip

The sample input and output files can be found in testfiles/rigidmol/3-electricfield.

Now you can easily perform a global optimization of the cluster $$\mathrm{HNO}_3\left(\mathrm{H}_2\mathrm{O}\right)_{10}$$. Basically, the following two files ef-0.inp and ef-0.cluster are needed:

ef-0.inp
1ef-0.cluster # cluster file name
230           # population size
350           # maximal generations
43            # scout limit
510.00000000  # amplitude
6ef-0         # save optimized configuration
730           # number of LMs to be saved

ef-0.cluster
12
2hno3.xyz    1
3tip4p.xyz   10
4* 10.0000


After copying misc/charmm/hno3.xyz and misc/charmm/tip4p.xyz to the current path, you can run the global optimization by:

$rigidmol ef-0.inp > ef-0.out  After a few seconds, You will find the global minimum in ef-0-OPT.xyz and local minima in ef-0-LM. So, what will $$\mathrm{HNO}_3\left(\mathrm{H}_2\mathrm{O}\right)_{10}$$ look like in an electric field, say $$F$$ = 0.8 V Å -1? We want to store the results in ef-8*, so first we prepare the input file ef-8.inp which is very similar to ef-0.inp: ef-8.inp 1ef-8.cluster # cluster file name 230 # population size 350 # maximal generations 43 # scout limit 510.00000000 # amplitude 6ef-8 # save optimized configuration 730 # number of LMs to be saved  Now prepare ef-8.cluster. You should add the electric field strength in the first line: ef-8.cluster 12 0.8 2hno3.xyz 1 3tip4p.xyz 10 4* 10.0000  Now you can run the global optimization by: $ rigidmol ef-8.inp > ef-8.out


Below are the global minima of $$\mathrm{HNO}_3\left(\mathrm{H}_2\mathrm{O}\right)_{10}$$ in vacuum and in the static electric field (ef-0-LM/0.xyz and ef-8-LM/0.xyz). Obviously, the electric field elongates the cluster.