I want to calculate the pressure for a p[articular region where with in a carbon nanotube can anyone tell me how should i proceed…

I want to calculate the pressure for a p[articular region where with in a

carbon nanotube can anyone tell me how should i proceed..........1. already i have chosen a region and then i calculate the stress/atom

2. But when from that i am going to calculate the pressure of that region by

the following commands its showing highly negative pressure...........variable volm_of_region equal (10.0*9.05*1.2124)

compute allperatom water stress/atom virial

compute allp water reduce/region inner sum c_allperatom[1]

c_allperatom[2] c_allperatom[3]

variable allpress equal

-(c_allp[1]+c_allp[2]+c_allp[3])/(3*${volm_of_region})I am getting a high negative value of pressure as a result...........

so? remember pressure is force per area and thus the sign is the

direction (i.e. inward or outward), so there is nothing bad about this

per se. whether the magnitude is reasonable or not is something that

depends on the simulation setup and choice of model.

Can anyone please suggest me anything............

test your formula on something where the result is known and if it is

working correctly, then you have a result. then it is a question

whether your choice of volume and selection of atoms is correct and

setup is correct. but that is something only you can figure out for

yourself.

axel.