How to calculate the liquidation price for MoonXBT perpetual contracts?

Liquidation occurs when the mark price hits the liquidation price.

Liquidation Price (Margin type: Isolated Margin)

Initial Margin Rate = 1/Leverage

The Tiered Margin is the basis for the Maintenance Margin Rate (MMR).

For Buy/Long:

Liquidation Price = Entry Price * (1 - Initial Margin Rate + Maintenance Margin Rate) 

Example:

Traders place a long entry of 1 BTC at 20,000 USDT with 50x leverage. 

Liquidation Price = 20,000 USDT * (1 - 2% + 0.5%) = 19,700 USDT

For Sell/Short:

Liquidation Price = Entry Price * (1 + Initial Margin Rate - Maintenance Margin Rate) 

Example:

Traders place a short entry of 1 BTC at 20,000USDT with 40x leverage. 

Liquidation Price = 20,000 USDT * (1 + 2.5% - 0.5%) = 20400 USDT

Liquidation Price (Margin type: Cross Margin)

Compared to Isolated Margin, the Liquidation Price under Cross Margin mode might keep changing as the available balance will be affected by the other trading pairs. Under cross margin mode, the system isolates the initial margin used for each position from the account balance, but the remaining balance is shared. The available balance will be affected by the unrealized P&L that occurred by all existing positions. Liquidation only happens when the available balance = 0 and each position does not have enough maintenance margin.

Example 

Under Cross Margin, assuming trader A holding a 1 BTC Long position at 20,000 USDT (100x leverage for BTC/USDT in Cross Margin).  The current available balance is 2,000 USDT, current mark price = 21,000 USD, unrealized profit (Mark Price) is 1,000 USDT.

Initial Margin = 20,000*1% = 200USDT

Maintenance Margin = 20,000*0.5% = 100USDT

Available Balance = 2,000USDT

Total Sustainable Loss = Available Balance + Initial Margin - Maintenance Margin

                                    = 2,000 + 200 -100 USDT

                                    = 2,100 USDT

With 2,100 USDT, the position can sustain a price loss of 2,100. Therefore, the liquidation price of this position would be 17,900 USDT (20,000-2,100). 

Using the logic above, we can derive the following liquidation price (Long). 

Current Mark Price (MP) - Liquidation Price (LP) = [Available Balance (AB) + Initial Margin (IM) - Maintenance Margin (MM)]/ Exposed Position Size (EPS)

LP (Long) = MP - (AB+IM-MM)/EPS

LP (Short) = MP+(AB+IM-MM)/EPS