Fix position of single atom or atoms during MC simulation

Dear EMC,

I’m going to run MC simulation with EMC program especially fix some of the atoms’ position
Maybe “simulation” part in build.emc file can work for it, but hard to know definite variable which is related to this optionMaybe “simulation” part in build.emc file can work for it, but hard to know definite variable which is related to this option

For example, I want to run MC simulation for with fix the position of first carbon in polyethylene.

It would be glad if you can help me.

Thank you!

Dear User,

You can set flags for each site by using the following command in EMC Script (i.e. your build.emc):

flag		= {oper -> set, select -> all,
	flag	-> {fix},
	site	-> {constant, ...},
	group	-> {constant, ...},
	cluster	-> {constant, ...},
	region	-> region};

In the above the flag → fix specifies a site as fixed in space (i.e. it is immobile and will not move). Furthermore, you can select either a site with a specific type, or a specific group or collection of groups, or a particular cluster. With region you can define a specific region within to apply your flags. All of these can either be included in or excluded from your flag command. The manual describes a bit more in depth what each of the options mean (see Scripting Commands → Flag). Please note that you can include EMC Scripting commands by adding

ITEM EMC

paragraphs to your .esh EMC Setup script.