Bsoft function

afm_simulate

Source:

src/img/img_afm.c

Description:

Simulates and AFM experiment.

Algorithm:

	The elastic force on an AFM tip is calculated as:

		F = kt*dz = kb*dV/d

	where	kt is the cantilever spring constant, typically 0.01 - 0.1 N/m.

			dz is the tip displacement due to specimen interaction.

			kb is the bulk modulus of the specimen, typically 1e9 N/m2.

			dV is the volume of the specimen displaced by the tip. This

				volume is here approximated as the density overlap volume.

			d is the specimen thickness in angstrom.

	The tip is positioned at each point (x,y,z) in the density map and the

	overlap volume calculated (i.e., a type of convolution).  This tip

	position corresponds to a zero displacement.  The correct tip position

	is found by shifting the tip upwards (in the z-direction) until the 

	displacement and elastic forces are approximately equal.  The tip 

	displacement is refined by interpolation and the force calculated.  

	The force map is returned in place of the original density map.

	Forces are calculated in piconewton. 

	The origin of the tip density is taken as nx/2, ny/2, 0.

Arguments:

Bimage* ptip	AFM tip density map - converted to force map.
Bimage* p	specimen density map.
float spring	AFM cantilever spring constant (N/m).
float modulus	bulk modules (N/m2).
float thick	sample thickness (angstrom).

Returns:

int 0.

Prototype:

int afm_simulate(Bimage* ptip, Bimage* p, float spring, float modulus, float thick)

Functions used:

balloc
bfree

Other objects included:

struct Bimage
constant VERB_

Generated by bdoc.pl on Mon Jun 15 11:47:14 2009

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