The title of your thread is: Change internal AREF.
1. AREF is a signal name attached with physical pin-21 of the ATmega328P MCU (Fig-1).
2. AREF is a pin by which you can feed external voltage (range: 1.1V to 5V) to the internal Vref-point of the ADC Module (Fig-2) when your not using internal 1.1V or 5V (Vcc) for the Vref-point.
3. AREF is a pin by which you can monitor the value of the voltage (either INTERNAL 1.1V or 5V/Vcc) that is connected with Vref-point of the ADC.
4. AREF is a pin between which and GND yu can connect an external establishing filter capacitor for the voltage of Vre-point of the ADC.
5. AREF stnads for what? Does it stand for AnalogREFErence? I have not found this name in the data sheets of the MCU.
6. AREF signal is different from the Arduino command/code: analogReference(arg) which means the of the argument (arg) is a voltage that is connected with the Vref-point of the ADC as per following Truth Table:
(1) analogReference(DEFAULT); //5V/Vcc will be connected with Vref-point of ADC.
(2) analogReference(INTERNAL); //Internal 1.1V will be connected with Vref-point of ADC.
(3) analogReference(EXTERNAL); //external variable voltage 1.1V to 5V could be feed via AREF-pin for the Vref-point of ADC.
7. Think to modify the little of the thread so that your intention is reflected. There is nothing such as internal AREF.