LTSpice (at least my version) doesn't have a crystal model per se. It has a crystal symbol, but you have to assign the various values for inductance, capacitance, and resistamce:
If you can't find a "proper" symbol in qucs, you might consider just using a capacitor symbol and specifying those characteristics.
I guess qucs is like ltspice I said you can use stuff from it I don't have the hang of it.
But it works so so I wanted to use LTspice but this is a linx box.
I've set up my own QUCS model for a crystal using the standard equivalent circuit. The attached example is for a 38 kHz tuning fork crystal. The parameters came from the manufacturer's datasheet. Note the extremely high inductance value. This is normal for a crystal.