.model statements

A .model statement is limited to defining parameters for a primitive SPICE device. 

.model statements follow the syntax:

.model <any model name> <device type> <a list of parameters>

For example, the following is a valid model for an NPN BJT: 

.model custom NPN
+IS=1.91e-15 BF=149.5 NF=0.91 VAF=10
+IKF=0.51821

The + character on each line is SPICE syntax for a continuation of a statement on a preceding line. 

Do not include any other text except for comments (lines that start with *) and white space. ';' is also comment delimiter.

For more information on .model statements for specific components, refer to  Multisim SPICE reference. 

Using a .model statement: 

1. Place one of the above components on the workspace.
2. Select the component and tap the configuration button   in the toolbar to open the configuration pane.
3. Select User-defined... from the Model drop-down. 
   For example, for a diode, select User-defined .model (D):  
    
   
4. Enter a valid .model statement in the text box, for example,  
    

Note. The body of the model definition can be optionally bracketed. 

For example,
.model myDiode d(
+ state1
+ state2
)

is the same as:
.model myDiode d
+ state1
+ state2